ByJ. E. Gore, F.R.A.S., Honorary Associate and Vice-President of the Liverpool Astronomical Society.
If we look up at the starry heavens on a clear, moonless night, all seems still, lifeless, and devoid of energy and motion. All of us are—or at least should be—familiar with the apparent diurnal motion of the star sphere, caused by the actual rotation of the earth on its axis, and with the slower annual motion, due to the earth's revolution round the sun, which brings different constellations into view at different seasons of the year. These motions, due to the great and universal law of gravitation, discovered and so ably expounded by the famous Sir Isaac Newton, are of course wonderful and orderly in their regularity, and bear silent testimony to the amazing power, majesty, and goodness of a great and glorious Creator. There are, however, other motions and changes, even still more wonderful, going on in the depths of space, which, though unperceived by the ordinary observer, have been revealed to the eye and contemplation of the astronomer by the accurate instruments and methods of research which modern science has placed at his disposal. Some accounts of these marvelous discoveries may prove of interest to the reader. The "fixed stars" are so called because they apparently hold a fixed position with reference to each other on the concave surface of the celestial vault, and do not, as far as the unaided eye can judge, change their relative positions as the planets do. Many stars have, however, what is technically called a "proper motion," which, though of course very minute, and only to be detected by the aid of refined and accurate instruments, yet accumulate in the course of ages, and sensibly alter their position in the sky. The largest "proper motion" hitherto detected (about seven seconds of arc per annum) is that of a small star in the constellation Ursa Major, known to astronomers as No. 1830 of Groonbridge's catalogue. It has been calculated that this star is rushing through space with the amazing and almost inconceivable velocity of 200 miles per second!—a velocity which would carry it from the earth to the sun in about 5½ days and to the moon in 20 minutes! The well-known double star 61 Cygni has a proper motion of about five seconds of arc per annum, both components moving through space together. This is, as far as yet known, the nearest star to the earth in the northern hemisphere. Its parallax, as determined by Sir R. S. Ball, is 0.4676 of a second of arc, and by Prof. Pritchard (by photography) 0.43 of a second. Taking the mean of these values, its distance from the earth would be about 460,000 times the earth's mean distance from the sun, and its actual velocity about 33 miles per second. This is, of course, the motion at right angles to the line of sight, but as it may also have a motioninthe line of sight, either to or from the eye, its real velocity is probably greater than this. The remarkable triple star 40 Eridani has a proper motion of four seconds annually. The components are a fourth magnitude star accompanied by a distant double companion which is a binary (or revolving double star), and accompanies the bright star in its flight through space. There are two other faint and distant companions which do not partake in the motion of the ternary star. In the year 1864 the bright star was situated to the east of a line joining these faint companions, but owing to its large proper motion it is now to the west of them. In the case of the triple star Struve 1516, one of the companions, which was to the west of the primary star in 1831, is, owing to the proper motion of the bright star, now to the east of it. Prof. Asaph Hall has found a parallax for 40 Eridani of 0.223 of a second. This, combined with the observed proper motion, indicates an actual velocity of about 54 miles per second. The star Mu Cassiopeiæ has also a large proper motion. This star, about 4,000 years ago, must have been close to Alpha Cassiopeiæ, and might have been so seen by the ancient astronomers. The proper motion of the bright star Arcturus is so considerable that in the course of about 30,000 years it will be near the equator, and about 10° to the north of the bright star Spica, from which it is at present separated by over 30°. These motions are of course those which take place across the face of the sky. There are, however, motions in the line of sight—both toward and from the eye—which have of late years been revealed to us by the spectroscope, that wonderful instrument of modern scientific research, by the aid of which several new metals have been discovered, and which has been found so useful in chemical analysis, and even in the manufacture of steel by the Bessemer process. Some years since, Dr. Huggins, the eminent spectroscopist, found that the bright star Sirius, "the monarch of the skies," was receding from the earth at the rate of about 20 miles a second. Later observations at Greenwich Observatory showed that this motion was gradually diminishing, and within the last few years it has been found that the motion of recession has been actually changed into a motion of approach, showing that this giant sun is probably traveling in a mighty orbit round some as yet unknown center of gravity.
From a consideration of stellar proper motions, it has been concluded that the sun—and therefore the whole solar system—is moving through space. Recent investigations make the velocity of translation about 19 miles per second (30 kilometers). The Greenwich observations place the "apex of the solar motion" (as the point toward which the sun is moving is called) between Rho and Sigma Cygni, while Dr. Huggins' results fix a point near Beta Cephei. Both these points are near the Milky Way.
There are other startling changes which have occasionally taken place among the stars, and which must be looked upon almost in the light of catastrophes. At rare intervals in the history of astronomy "temporary" or "new" stars have suddenly blazed out in the heavens which were previously either unknown to astronomers, or else were invisible, except in the telescope. Some of these were of great brilliancy. In A.D. 173 a bright star is recorded in the Chinese annals as having appeared between Alpha and Beta Centauri (two bright stars in the southern hemisphere). It remained visible for seven or eight months, and is described as resembling "a large bamboo mat" (!)—a not very lucid description. It is worthy of remark that there exists at the present time, close to the spot indicated, an interesting variable star, which may possibly be identical with the bright star of thesecond century. Perhaps the most remarkable of these wonderful objects was that observed by the famous Tycho Brahe in 1572, in Cassiopeia, and called the "Pilgrim." It was so brilliant that it rivaled the planet Venus at its brightest, and was visible at noonday. It remained visible for over a year and then disappeared.
A small star close to its recorded position has been observed in recent years, and as it is thought to be slightly variable in its light, it may possibly be identical with the long lost star of Tycho Brahe. Another new star of almost equal brilliancy was observed in October, 1604, in Ophiuchus, a few degrees southeast of the star Eta Ophiuchi. The planets Mars, Jupiter, and Saturn were close together in this vicinity, and one evening Mostlin, a pupil of Kepler's, remarked that a new and very brilliant star had joined the group. When first seen it was white, and exceeded in brightness Mars and Jupiter, and was even thought to rival Venus in splendor! It gradually diminished, however, and in six months was not equal in luster to Saturn; in March, 1606, it had entirely disappeared. In 1670 a star of the third magnitude was observed by Anthelm near Beta Cygni. It remained visible for about two years, and increased and diminished several times before it finally disappeared. Flamsteed's star, No. 11 of Vulpecula, has been supposed to be identical with Anthelm's star, but Baily could not find that such a star exists. A small star has, however, been observed at Greenwich within one minute of arc of the place assigned to the temporary star by Picard's observations.
Variability has been suspected in this faint star, and according to Hind it has a hazy, ill-defined appearance about it, which may perhaps suggest that it may be a small planetary nebula, similar to Schmidt's new star of 1876 in Cygnus. A small new star was observed by Hind in Ophiuchus on April 28, 1848. When first noticed it was about the fifth magnitude. It afterward rose to about fourth magnitude, but very soon faded away, and, although still visible in the telescope, has become very faint in recent years. A new star of seventh magnitude was found by Pogson on May 28, 1860, in the well-known star cluster known as 80 Messier in Scorpio. The light of the star when first seen obscured the light of the nebula. On June 10 the star had nearly disappeared, and the nebula was again seen shining with great brilliancy.
A very interesting temporary star—known as the "Blaze Star"—suddenly appeared in Corona Borealis in May, 1866. It was first seen by the late Mr. Birmingham, of Tuam, Ireland, on the night of May 12, when it was of the second magnitude and equal in brightness to Alphecca, the brightest star in the well-known "Coronet." It must have made its appearance very suddenly, for Dr. Schmidt, the director of the Athens observatory, stated that he was observing this region of the heavens a few hours previously, and noticed nothing unusual. It rapidly diminished in brightness, and on May 24 of the same year was reduced to nearly the ninth magnitude. It was soon discovered that the star had been previously observed, and its place registered by the great German astronomer, Argelander, as of magnitude 9½, so that it is possibly a variable star of irregular period and fitful variability. When near its maximum brilliancy, its light was examined by Dr. Huggins with the spectroscope, which showed the bright lines of incandescent hydrogen gas in addition to the ordinary stellar spectrum. This implies that the great increase in its light was due to a sudden outburst of hydrogen in the star's atmosphere. Some observers remarked that when viewed with the naked eye it decidedly twinkled more than other stars in the neighborhood, which rendered a correct estimate of its relative brightness somewhat difficult. During the years 1866 to 1876, Schmidt detected variations of light which seemed to show a period of about 94 days, and these observations were confirmed by Schonfeld.
On the evening of November 24, 1876, the late Dr. Schmidt, of Athens, discovered a new star of the third magnitude, near Rho Cygni, in a spot where he was certain that no bright star was visible four nights previously. When first seen, it was somewhat brighter than Eta Pegasi. It did not, however, remain long at this degree of brightness, but rapidly decreased, and on November 30 had faded to fifth magnitude. It afterward diminished very regularly, and in September, 1885, was estimated only fifteenth magnitude with the 15½ inch refractor of Mr. Wigglesworth's observatory. The star was examined with the spectroscope a few days after its discovery, and showed bright lines similar to the "Blaze Star" in the Northern Crown. One of these bright lines was believed to be identical with Kirchhoff's No. 1474, which has been observed in the spectrum of the solar corona during total eclipses of the sun. This star would seem to be quite new, as there is no star in any of the catalogues in its position. In September, 1877, it was examined with the spectroscope at Lord Crawford's observatory, and its light was found to be almost entirely monochromatic (of only one color), showing that the star "had changed into a planetary nebula of small angular diameter" (!)
In August, 1885, a star of about seventh magnitude made its appearance close to the nucleus of the Great Nebula in Andromeda—a well-known object visible to the naked eye, and which has been well called "the Queen of the Nebulæ." The new star was independently discovered by several observers toward the end of August, but seems to have been first certainly seen by Mr. T. W. Ward, of Belfast, on August 19, at 11 P.M. At Greenwich observatory the spectrum of the new star was found "of precisely the same character as that of the nebula,i. e., it was perfectly continuous, no lines, either bright or dark, being visible, and the red end was wanting." Dr. Huggins, however, on September 9, thought he could see from three to five bright lines in its spectrum. The star gradually faded away, and on February 7, 1886, was estimated only sixteenth magnitude in the 26 inch refractor of the naval observatory at Washington. From a series of measures by Prof. Asaph Hall he found "no certain indications of any parallax," so that evidently the star and the nebula, in which it probably lies, are situated at an immense distance from the earth. Prof. Seeliger has investigated the decrease in light of the star on the hypothesis that it was a cooling body, which had been suddenly raised to an intense heat by the shock of a collision, and finds a fair agreement between theory and observation. Anwers points out the similarity between this outburst and the new star of 1860 in thecluster 80 Messier, and thinks it very probable that both phenomena were due to physical changes in the nebulæ in which they occurred.
With reference to the colors of the stars, some of the red stars have been suspected to vary in color. The bright star Sirius is supposed—from the description of it by ancient astronomers—to have been originally red, but this seems very doubtful. The Persian astronomer Al Sufi, in his "Description of the Heavens," written in the tenth century, describes the well-known variable star Algol distinctly as a red star. It is now white, and this is perhaps the best attested instance on record of change of color in a bright star.—Naturalists' Monthly.
ByFrederick Leroy Sargent.
In the various names which the dandelion has received, we see expressed, for the most part, either a reference to the tooth-like recurved lobes of the leaves, Fig. 1, or an allusion to the medicinal properties of the plant. Thus, our English name is a modified form of the Frenchdent de lion, meaning lion's tooth, and in German we have the same idea expressed inLöwenzahn. Fifty years ago this plant appeared in the botanies asLeontodon taraxicum, the generic name being derived from the Greekleon, lion, andodons, tooth, and the specific from the Greektarasso, to stir up, in reference to the effect of a dose. In later works we find the genusLeontodon, including the "fall dandelion" (L. autumnale), but not the true dandelion, which now appears in a genus by itself under the nameTaraxicum Densleonis. Here the specific name is merely "lion's tooth" again, in Latin.
Outline of leaf.Fig. 1.
Finally, in the latest works our plant is given asTaraxicum officinale, since this has been found to be the name which, according to the rules of botanical nomenclature, takes precedence of all others. An allusion to the teeth is thus no longer retained, the only reference remaining being to the plant's officinal use.
To the majority of people the mention of the dandelion calls to mind not so much its medicinal properties as its use for food. Although its cultivation, either as a spring pot herb or as a salad with blanched leaves, is comparatively modern, the wild plant seems to have been long valued as a vegetable. There is reason to believe that the Romans made use of it as a pot herb, and Chinese writers of the fourteenth century mention its being eaten in their country, although there is no evidence of cultivation at that time.
There are but few of our flowering plants that grow so widespread over the world. It occurs in North America from the Atlantic to the Pacific coast, in Europe, in Asia, and in the Arctic regions. This extensive range may in part be accounted for by the fact that our plant belongs to the large and aggressive family of theCompositæ, and is thus related to such invaders as daisies, burdocks, and thistles. Still, the dandelion has more to recommend it than mere family connection; for, despite its lowly aspect, it is no poor relation, but, as we shall hope to show in the present article, it has many virtues of its own which entitle it to respect.
Prominent among these is its adaptability to the different conditions under which it grows. It seems to make the best of everything. If by chance a seed falls upon poor, thin soil, the young plant sends forth, as rapidly as possible, a rosette of leaves pressed close to the earth. And thus, on the principle that "possession is nine points of the law," it secures for its roots the use of a certain amount of territory quite safe from the encroachments of other plants. In rich ground the case is quite different, for here there is so much nutriment in a small quantity of earth, that the struggle for soil is not such a life and death matter as in the less favored localities. Consequently we find a large number of plants crowded together as close as they can stand; and it is obvious that if, under these circumstances, the dandelion should develop a flat rosette of leaves, the grass and other plants growing around would soon overshadow it, and it would have small chance for life.
Our plant, therefore, extends its leaves upward, and does its best to elongate them so as to keep pace with the growth of its rivals. But as these are for the most part grasses and plants which grow by elongation of the stem, the race for sunshine is rather in favor of these other plants, for the reason that a given amount of material put into a stem makes a stiffer organ than when put into a leaf. Still, even with these odds against it, the dandelion seems well able to hold its own, for it probably derives more or less advantage from the recurved lobes, or teeth, which give the plant its name. These are admirably fitted to act in much the same manner as a ratchet; and when the neighboring grasses are blown against the dandelion, a blade may slide along the margin of the leaf toward the base; but, as it springs back from its own elasticity, it cannot slide in the opposite direction, for a tooth will catch it, and thus force it to help support the leaf, and hold it up to the sunshine. We need not stop to consider how the dandelion behaves in soil which is neither very rich nor very poor, for enough has been said to show that it has not much to fear from any rivals it may meet under ordinary circumstances.
It is not only against the aggressions of neighboring plants, however, that our dandelion needs to be prepared.It is at least equally important for its welfare that it have some means of protection against herbivorous animals—not only such as might eat its leaves, but also the more stealthy ones that live upon the food which plants store underground. All such foes it thwarts by a means as simple as it is efficient. Every part of the plant contains a milky juice which is intensely bitter, and a first taste is quite enough to convince the most stupid animal that raw dandelion is not good eating, and most animals know enough to let it severely alone. Curiously enough, however, in this, as in many other cases, it happens that what in nature acts to deter animals from eating the plant, with man offers the chief attraction, for it is this very bitter principle (taraxacin) which gives to dandelion greens their peculiar flavor, and affords the essential element in the extract which physicians prescribe.
The store of food, referred to above, which the dandelion accumulates in its root, not infrequently enables it to pass, almost unharmed, through dangers that with less provident plants would surely prove fatal. For example, it must often happen that from drought or from being trampled upon by animals, the leaves become wholly or in part destroyed. Now, if there were no reserve store of food, the plant would have no chance of rallying; but as it is, this food supplies the material for new growth, and upon the return of favorable conditions, fresh leaves are developed, and the plant lives on as before. Primarily, of course, the purpose of this storage of food is to enable the plant to live on from year to year, resting in the winter, and in the spring beginning work again with a good start.
In comparing the higher with the lower plants, the superiority of the former is most beautifully shown in the better provision which is made for the welfare of offspring; and in this regard our dandelion stands among the highest. Before we can understand the ways in which our little plant performs this part of its life work, we must briefly consider the structure of the blossom.
Diagram of structure.Fig. 2.
If with a sharp knife we cut a blossom in halves, from the stem upward, the parts represented in Fig. 2 will be disclosed. Surmounting the stalk is a cushion-like receptacle, R, from the top of which arise a number of tiny flowers, F, while from the side grow out a series of green scales, S, forming an involucre around the whole. A single one of these florets, Fig. 3, exhibits the following parts: First, a bright yellow corolla, C O, tubular below, but strap-shaped above, as if a tube had been split for part of the way on one side, and the upper part flattened. Second, five stamens, S K, attached by slender filaments, F M, to the tubular part of the corolla, and with their anthers or pollen sacs, A N, joined together by the edges to form a tube. Third, a single pistil having a long style, S Y, which, above, passes through the anther tube, and bears at its end two diverging stigmas, S G, and below connects by a short neck, N, with the small ovary, O, which contains a solitary ovule. Fourth, a calyx, C X, composed of numerous slender bristles.
Drawing of structure.Fig. 3.
The purpose of these complex structures is, of course, in one way or another to secure the development of the ovule into a seed fitted to produce a new plant. This development will proceed only after the ovule has been influenced (i. e., fertilized) by pollen placed upon the stigma; but when once the mysterious process of fertilization has taken place, then there follows immediately those wonderful changes in the blossom which culminate in the ripening of the fruit.
There are but two possible ways in which fertilization may be secured; either the pollen which affects the ovule must come from the same flower (then called close fertilization), or the pollen must come from another flower of the same kind (cross fertilization). Now, while either of these methods will insure the production of a seed, numerous experiments go to show that those offspring which result from cross fertilization are in many ways superior to those which are produced from close fertilization; and it is to the advantages of cross fertilization that we have to look for an explanation of the significance of many peculiar structures, not only of the dandelion, but of flowers in general.
It is obvious that, to secure cross fertilization, there must be some agent to transfer the pollen from one plant to another. Most commonly, either the wind is taken advantage of for this purpose, as with elms, pines, grasses, etc., or else flying insects are induced to perform the office, as is the case with the majority of our familiar flowers. The wind is a very wasteful carrier,so that for every grain that is properly placed, thousands, or even millions, may be lost. Insects, on the contrary, waste but little; and, moreover, as Aristotle so shrewdly observed, they habitually confine their visits, for a number of trips, exclusively to the flowers of one species.
The dandelion seems to fully appreciate the great advantages of securing the services of insects, for it appeals most strongly to their love of bright colors and their passion for sweets. As the flowers open, each tiny golden cup is filled to the brim with purest nectar, and he must be a very dull insect, indeed, that cannot see the brilliant head of flowers as far as he can see anything. At any rate, it is not the dandelion's fault if he does not, for the blossom is placed where it will be as conspicuous as possible. If the surrounding herbage is tall, the flower stalk is elongated, so that the crown of flowers may not be obscured. If the plants around are low-lying, it would be wasteful to have a long stalk, so it has a short one, sometimes so short that the blossom looks like a button in the center of the leaf rosette. Economy of material is furthermore shown in the fact that the stalk is always hollow, for it is a principle well known to builders that, when there is required a pillar of a given strength, less material is needed for the tubular form than for the solid cylinder.
Drawing of structure.Fig. 4.
Drawing of structure.Fig. 5.
But to return to our flower. We have next to consider how the visits of insects are utilized to secure cross fertilization. If we examine the anther tube of a flower that has just opened, Fig. 4, we shall see that the style has not yet protruded, but fills the entire cavity, except such space as is occupied by a quantity of pollen which the anthers have shed. So much of the style as is within the tube is thickly beset with hairs that point upward; and when the lower portion elongates, this hairy part brushes the pollen out of the tube, and protrudes, covered with the yellow dust, Fig. 5. At this stage, an insect coming for nectar must rub against the style, and so become more or less covered with pollen. None of it, however, can get upon the stigmas, for they are not yet exposed. After a short time has elapsed, during which much of the pollen has probably been rubbed off, the style is seen to split at the top; and as the halves separate and roll back, Fig. 3, their inner faces (the stigmas) are exposed. If, now, the flower be visited by an insect which has previously been to a younger flower, the pollen he brings will be deposited upon the stigmas as he rubs against them, and cross fertilization will be effected.
Let us suppose, however, that no insect visits the blossom—and this must often happen to such as appear very early in the spring or late in the fall, when hardly any insects are around. In such cases we find that seeds are produced, and therefore we must infer that fertilization has in some way or other been secured. An examination of a flower still older than any we have considered, Fig. 6, will show us what takes place. Here it will be seen that, after the stigmas have diverged, they continue to roll back, until a coil of one or more turns has been made; and as a result of this the stigmatic surface comes in contact with the hairs on the style, and touches the pollen grains entangled by them. Still, the close fertilization thus accomplished is only a last resort, and it can only occur in the event of insects' visits having failed; for when pollen from another flower has once fallen on the stigma, no pollen coming afterward can have the least effect. Thus, we have another instance of the dandelion's ability to make the best of its surroundings.
Drawing of structure.Fig. 6.
It even adapts itself to the weather; for when the sun shines, the scales of the involucre bend back, and the blossom is expanded to its fullest extent; but in dull weather, or at night, the scales bend inward, and the blossom is tightly closed. The advantages of this remarkable movement, with its implied sensitiveness, is obvious when we consider that insects are abroad only in sunshine, while at other times there is danger of dew or rain getting into the nectar, and so spoiling it for the insects.
After fertilization has been accomplished throughout the blossom, the involucre closes, and remains closed during the ripening of the fruit. The changes which now take place are as follows: In each flower the corolla, stamens, and style, being of no further use, wither, and sever their connection with the ovary; the ovule develops into a seed containing a tiny plantlet well provided with food for its use during germination;the ovary grows to keep pace with the seed, its tissues become hardened, and a number of spine-like projections develop near the upper part; and finally the short neck which bears the calyx bristles elongates, pushing upward the withered parts of the flower. At this stage the involucral scales bend back through an arc of about 180°, the cushion-like receptacle becomes almost spherically convex, the fruits radiate in all directions, the bristles spread, and a beautiful cluster of little parachutes is presented to the wind.
Drawing of structure.Fig. 7.
Drawing of structure.Fig. 8.
Even a glance at one of these fruits, Fig. 7, is sufficient to discover a wonderful fitness for transportation by wind, and more careful study shows that this fitness pervades every detail. For example, on examining the bristles microscopically, Fig. 8, it is shown that they are not simple threads, but each is hollow and has numerous projections extending on either side, all of which serves to increase the buoyancy in a very effective way.
The experience of aeronauts has shown that a highly important part in the equipment of a balloon, after the attainment of buoyancy, is the provision of some means of arresting the balloon's progress when the destination has been reached. One of the most successful means which they employ is the grappling hook; and as we find the base of our diminutive parachute provided with a number of upwardly directed spines, it seems fair to conclude that these serve to arrest the fruit upon favorable soil. If it comes to rest upon a smooth surface—which, of course, would be barren—the next breeze would easily blow it away; but if it chance to fall on soil or among other plants, the effect of the spines would be to retain it against the power of even a strong wind. Thus, we may leave it safely landed upon good soil, ready to begin under favorable conditions the cycle of its wonderful life.—Popular Science News.
ByDr. C. V. Riley.
There is always a great deal of interest attaching to organisms which are unique in character and which systematists find difficulty in placing in any of their schemes of classification. A number of instances will occur to every working naturalist, and I need only refer to Limulus, and the extensive literature devoted, during the past decade, to the discussion of its true position, as a marked and well-known illustration. In hexapods the common earwig and flea are familiar illustrations. These osculant or aberrant forms occur most among parasitic groups, as the Stylopidæ, Hippoboscidæ, Pulicidæ, Mallophaga, etc. Probably no hexapod, however, has more interested entomologists thanPlatypsyllus castorisRitsema, a parasite of the beaver. I cannot better illustrate the diversity of opinion respecting its true position in zoology than by giving an epitome of the more important literature upon it.
[12]Read at the meeting of the National Academy of Sciences, April 20, 1888.
[12]Read at the meeting of the National Academy of Sciences, April 20, 1888.
J. Ritsema, inPetites Nouvelles Entomologiquesfor September 15, 1869, described the species asPlatypsyllus castoris. He found it on some American beavers (Castor canadensis) in the zoological garden of Rotterdam. He considered it to "undoubtedly" belong to the Suctoria of De Geer, and to form a new genus of Pulicidæ.
In the same year, in theTijdschrift voor Entomologie, 2d ser., vol. v., p. 185 (which I have not seen), the same author publishes what is apparently a redescription of the insect. He gives his views more fully as to its systematic position, considering that it belongs to the Aphaniptera, and is equivalent to the Pulicidæ.
In the same year, Prof. J. O. Westwood (having previously read a description of the species, November 9, 1868, before the Ashmolean Society of Oxford) published in theEntomologist's Monthly Magazine, vol. vi., October, 1869, pp. 118-119, a full characterization of the insect under the name ofPlatypsyllus castorinus. A new order,Achreioptera, is established upon the species, which he very aptly likens, in general appearance, to a cross between a flattened flea and a diminutive cockroach. "The abnormal economy of the insect, its remarkable structure, the apparent want of mandibles, our ignorance of its transformations, and the possibility that the creature may be homomorphous in the larva and pupa states," are the reasons assigned for establishing the new order, and here Prof. Westwood is perfectly consistent, as in his famous "Introduction to the Classification of Insects" the Forficulidæ are placed in the order Euplexoptera; the Thripidæ in the order Thysanoptera; the Phryganeidæ in the order Thrichoptera; the Stylopidæ in the order Strepsiptera; and the Pulicidæ in the order Aphaniptera.
In 1872, Dr. J. L. Le Conte published his paper "OnPlatypsyllidæ, a New Family of Coleoptera" (Proc. Zool. Soc. of London for 1872, pp. 779-804, pl. lxviii.), in which he shows thatPlatypsyllais undoubtedly coleopterous and cannot possibly be referred to the Aphaniptera. Careful descriptions and figures of anatomical details are given, and he finds that its affinities are very composite, but in the direction of the Adephagous and Clavicorn series. Its most convenient place isshown to be between theHydrophilidæandLeptinidæ. There seems to be no good reason why the namePlatypsyllusis here changed toPlatypsylla, a spelling adopted by most subsequent American writers.
In 1874, Prof. Westwood, in the "Thesaurus Entomologicus Oxoniensis" (Oxford, 1874), p. 194, pl. xxxvii., gives figures with details; reprints his previous diagnosis, and maintains his previous course in erecting a new order for the insect, without giving any additional reasons.
In 1880, P. Megnin, in "Les Parasites et les maladies parasitaires," etc., Paris, 1880, gives (pp. 66-67) a description of the family "Platypsyllines" without expressing an opinion concerning the systematic position. He also describes and figures the species.
In 1882, Dr. Geo. H. Horn (Trans. Amer. Ent. Soc., x., 1882-83; Monthly Proc., Feb. 10, 1882, p. ii.) exhibited drawings illustrating the anatomy ofPlatypsyllaandLeptinus, and showed that a close relationship exists between these genera. Later, in his "Notes on Some Little Known Genera and Species of Coleoptera" (Trans. Amer. Ent. Soc., x., 1882-83, pp. 113-126, pl. v., 114-116), he reviews the characters, and explains and illustrates the anatomical details. The differences he points out between his observations and those of Le Conte are more particularly in the mandibles. In connection with this paper he also describes and illustrates the structure of Leptinillus, which he separates from Leptinus, and demonstrates their close relationship with Platypsyllus.
In 1883, Le Conte and Horn, in their "Classification of the Coleoptera of North America" (Washington, Smithsonian Institution, 1883), give (pp. 13-15) a full description of the family characters, a little modified from Le Conte's first description, but sustaining his views on the systematic position ofPlatypsyllidæ.
In 1883, Alphonse Bonhoure (Ann. Soc. de France, 1883; Bull, des Seances, p. cxxvi.) exhibited drawings and specimens ofPlatypsyllus castorisfound in theDepartement des Bouches du Rhone.
In 1884, Edm. Reitter, in "Platypsylla castorisRits. als Vertreter einer neuer europaischen Coleopteren-Familie" (Wiener entom. Zeit. iii., 1884, pp. 19-21) gives a lengthy description of the species with special regard to the sexual differences. He shows that the European insect is not specifically distinct from the American form, but he does not express an opinion on the position of the family among the Coleoptera.
In the same year, Bonhoure (Ann. Soc. Ent. de France, 1884, pp. 143-153) more fully records its discovery onCastor fibertaken in the Petit-Rhone. It is a question whether this European beaver, now quite rare, is distinct from ours. He gives a very good review of the subject, with a plate of the most important details, after Horn, and he fully indorses the coleopterological position of the insect.
In the same year Ritsema (Tijdschrift voor Entomologie, 1883-84, lxxxvi.) refers to Bonhoure's discovery ofPlatypsyllain France, and corrects Reitter in some unimportant details.
In 1885, Reitter, in "Coleopterologische Notizen" xiii. (Wiener entomolog. Zeit., vol. iv., 1885, p. 274), answers Ritsema's criticism.
In the same year, Dr. Friederich Brauer, in his masterly "Systematisch-zoologische Studien" (Sitzh. der Kais. Akad. der Wissensch., xci., p. 364), speaks of the relationship in the thoracic characters between Mallophaga and Coleoptera as illustrated by Platypsyllus, by inference admitting the coleopterous nature of the latter, but recognizing that it has mallophagous affinities.
In 1886, H. J. Kolbe, in his "Ueber die Stellung von Platypsyllus im System" (Berlin entom. Zeitsch., xxx., 1886, pp. 103-105), discusses the subject, without any new evidence, however. He concludes that most of its characteristics relate it to the Corrodentia, and particularly to the sub-order Mallophaga, in which it has its closest kinship in Liotheidæ. The remarkable tripartite mentum he thinks should not be compared with the bipartite mentum of Leptinus, and calls attention to the fact that in Ancistrona in Mallophaga it is also trilobed.
The above are the more important papers on the subject, though the insect has been referred by other authors to both Neuroptera and Orthoptera.
LARVA.LARVA OF PLATYPSYLLUS CASTORIS—DORSAL VIEW.
Platypsyllus Castoris.PLATYPSYLLUS CASTORIS.
Where the characters of the image have been so often described, it is unnecessary to refer to them in detail, and I will only call attention to the more striking structural features and to some omissions by, or differences between, previous authors. A glance at the illustrations which I have prepared will show the prevailing characteristics of this interesting creature, its generalovoid and flattened form, and more particularly the flattened semicircular head. Dorsally, we notice the rather prominent occiput fringed behind with short and broad depressed spines or teeth which form a sort of comb, the prothorax trapezoidal and but very slightly curved, with side margins strongly grooved. There is a very distinct scutellem, and the two elytra are rounded at the tip and without venation. Hind wings and eyes are both wanting. The abdomen shows five segments, each with a row of depressed bristles.
On the ventral surface we find among the more curious characteristics, first the antennæ; these were originally described by Westwood as three-jointed, the club being annulated. Le Conte could not distinctly make out the number of annular joints upon this club, though he thought he detected seven, which made nine joints to the whole antenna. The club is received in the deep cup-shaped excavation of the second joint. Horn thought he detected a division of the second joint, and resolved but six segments in the club, making also nine joints to the whole antenna, but in a somewhat different fashion from Le Conte. Westwood's figure shows eight annuli to the club. He failed to find any trace of the mandibles, but Le Conte described them as small, flat, subquadrate, with the inner side deeply crenulate, and resembling those ofCorylophus; the stipes well developed, and biarticulate. Horn could not entirely make out the mandibles as described by Le Conte, and rather concluded that what Le Conte described is really one of the granules which occur behind the labrum. He considered that the piece could hardly be even an aborted mandible, because of its diminutive size.
Young Larva.YOUNG LARVA.
What all authors have agreed in calling the mentum is very noticeable, being large and broad, and trilobed behind. The maxillæ are strong, with complicated stipes and with two flat, thin lobes, the inner one smaller than the outer and rounded at the tip, both lobes being ciliate. The maxillary palpi are four-jointed, the labial palpi three-jointed. The prosternum is very large, subtriangular, concealing the insertion of the coxæ, and extending over the front part of the mesosternum, as does this over the front of the metasternum. Six ventral segments of the abdomen are visible behind the posterior coxæ, which conceal two and the base of a third. The coxæ are flat and not at all prominent. The legs are characterized by broad and flattened tibiæ and femora, and the strong spines with which they are armed. The tarsi are five-jointed, the front and middle pair with a row of claviform membraneous appendages each side, which Le Conte found only in the male.
American entomologists have been satisfied to follow Le Conte and Horn as to the position of Platypsyllus. Yet with such diversity of opinion on the subject among high European authorities, the importance of a knowledge of the adolescent states has been recognized, as the character of either the larva or pupa would settle the question.
During a stay at West Point, Neb., in October, 1886, I learned from one of my agents, Mr. Lawrence Bruner, that there was a beaver in a creek not far from that point, and I at once made arrangements for him to trap the beaver, and to look particularly for living specimens of Platypsyllus on the skin, and especially the earlier stages. He succeeded in capturing the beaver and sent me some fifteen specimens of the larva and also some imagos, but neither eggs nor pupæ were found. A glance at the larva satisfied me at once of its coleopterous nature; but as we have, waiting to beworked up and published, anembarras de richesses entomologiquesin the collections of the National Museum, and as circumstances largely decide the precedence, I should probably not have called attention to this larva for some time, had it not been that at the last monthly meeting of the Entomological Society of Washington, Dr. Horn, who was present, announced the finding, the present spring, by one of his correspondents, of this very larva, and exhibited a specimen. Some points about it, and especially the position of the spiracles, being yet rather obscure in his mind, he requested me to examine my material, which I have thus been led to do. I have made a figure of this larva which will sufficiently indicate its nature.
The general form of the trophi, and particularly the anal cerci, fully settle the disputed point, and remove this insect completely from the Mallophaga (none of which possess them), and confirm its position in the Clavicorn series of the Coleoptera. Yet in the larva, as in the imago, the effects of its parasitic life are shown in certain modifications which approach the running section of the Mallophaga. Without going into details I may say that, besides its general and more decided coleopterological features, this larva is distinguished by the shortness and stoutness of its legs, by the size and stoutness of the antennæ, by the stiff and long depressed hairs on the dorsal and more particularly on the ventral surface, and by the dorsal position of the abdominal spiracles, all characters approaching the Mallophaga. The first pair of spiracles is lateral, and may be said to be mesothoracic, being placed on the mesothoracic joint, but on a distinct fold. The eight abdominal spiracles are placed on the sides of the dorsum, and in this respect recall the parasitic triungulin of the meloid larvæ. The mandibles are barely corneous, and they are more elongate and curved in the younger than in the older larva, while the legs are also relatively stouter, more curved, and with a much longer and sharper claw in the younger larva, which seems well fitted for grasping the hairs of its host.
There can no longer be any doubt, therefore, about the true position of Platypsyllus. The eggs will probably be found attached in some way to the hairs of the animal they are laid on, much as they are in Mallophaga, and the pupa is probably formed in the nests of the host, and not upon the skin, which will explain the reason for its not occurring with the larva and imago upon the beaver, either in the case of my specimens or those of Dr. Horn.
The greatest resemblance of Platypsyllus in the imago state to the Mallophaga is found in the spinous comb on the hind border of the occiput, the arrangement of the spines on the abdomen, and the superficial antennal structure, but particularly in the broad trilobed mentum. All of the other characteristics are readily referable to the Coleoptera, though, as Le Conte pointed out, they are composite, recalling in the antennæ the Grynidæ, in the pronotum the Silphidæ, in the mesosternum Limulodes, in the elytra the Staphilindæ, in the legs the Anisotomidæ, and in the mandibles the Corylophidæ. The scutellum and the five-jointed tarsi at once remove it from Mallophaga, and it is a wonder that Le Conte and Horn have not more fully insisted on this fact. The trophi are very complicated, and there are various details of structure not noticed or not mentioned by any of the writers upon the subject hitherto.
I have been led to very carefully examine the imago, and the more closely I have done so, the more completely I realize the accuracy of Le Conte's original work. The mandibles are visible or not, according as they are exposed or withdrawn, and their existence may depend on the sex, as, so far as my material justifies conclusion, they are visible in the male only. Where found they correspond to Le Conte's description. Even in the larva they are weak and of doubtful service in mastication, while in the imago they are, as is also the labrum, quite rudimentary, which fact hardly justifies us, however, in arguing their non-existence.
As confirmatory of the affinities of Platypsyllus, as here proved, it may be mentioned thatLeptinus testaceousMull., the only species of its genus, is known to be parasitic on mice, as it has been found upon them in Philadelphia by Dr. Jno. A. Ryder, and I have taken it in the nests of a common field mouse near Washington. But still more interesting is the fact thatLeptinillus validusHorn (also the only species of its genus) is an associate parasite of Platypsyllus on the beaver, a number of both having been taken by one of my agents, Mr. A. Koebele, in San Francisco, from beaver skins brought from Alaska.