The Thysanura, as the Poduras and their allies, the Lepismas, are called, have been generally neglected by entomologists, and but few naturalists have paid special attention to them.[9] Of all those microscopists who have examined Podura scales as test objects, we wonder how many really know what a Podura is?

In preparing the following account I have been under constant indebtedness to the admirable and exhaustive papers of Sir John Lubbock, in the London "LinnÆan Transactions" (vols. 23, 26 and 27). Entomologists will be glad to learn that he is shortly going to press with a volume on the Poduras, which, in distinction from the Lepismas, to which he restricts the term Thysanura, he calls Collembola, in allusion to the sucker-like tubercle situated on the under side of the body, which no other insects are known to possess.

The group of Bristle-tails, as we would dub the Lepismas in distinction from the Spring-tails, we will first consider. They are abundant in the Middle States under stones and leaves in forests, and northward are common in damp houses, while one beautiful species that we have never noticed elsewhere, is our "cricket on the hearth," abounding in the chinks and crannies of the range of our house, and also in closets, where it feeds on sugar, etc., and comes out like cockroaches, at night, shunning the light. Like the cockroaches, which it vaguely resembles in form, this species loves hot and dry localities, in distinction from the others which seek moisture as well as darkness. By some they are called "silver witches," and as they dart off, when disturbed, like a streak of light, their bodies being coated in a suit of shining mail, which the arrangement of the scales resembles, they have really a weird and ghostly look.

The most complicated genus, and the one which stands at the head of the family, is Machilis, one species of which lives in the Northern and Middle States, and another in Oregon. They affect damp places, living under leaves and stones. They all have rounded, highly arched bodies, and large compound eyes, the two being united together. The maxillary palpi are greatly developed, but the chief characteristics are the two-jointed stylets arranged in nine pairs along each side of the abdomen, reminding us of the abdominal legs of Myriopods. The body ends in three long bristles, as in Lepisma.

The Lepisma saccharina of LinnÆus, if, as is probable, that is the name of our common species, is not uncommon in old damp houses, where it has the habits of the cockroach, eating cloths, tapestry, silken trimmings of furniture, and doing occasional damage to libraries by devouring the paste, and eating holes in the leaves and covers of books.

In general form Lepisma may be compared to the larva of Perla, a net-veined Neuropterous insect, and also to the narrow-bodied species of cockroaches, minus the wings. The body is long and narrow, covered with rather coarse scales, and ends in three many jointed anal stylets, or bristles, which closely resemble the many jointed antennÆ, which are remarkably long and slender. The thermophilous species already alluded to may be described as perhaps the type of the genus, the L. saccharina being simpler in its structure. The body is narrow and flattened; the basal joints of the legs being broad, flat and almost triangular, like the same joints in the cockroaches. The legs consist of six joints, the tarsal joints being large and two in number, and bearing a pair of terminal curved claws. The three thoracic segments are of nearly equal size, and the eight abdominal segments are also of similar size. The tracheÆ are well developed, and may be readily seen in the legs. The end of the rather long and weak abdomen is propped up by two or three pairs of bristles, which are simple, not jointed, but moving freely at their insertion; thus they take the place of legs, and remind one of the abdominal legs of the Myriopods; and we shall see in certain other genera (Machilis and Campodea) of the Bristle-tails that there are actually two-jointed bristles arranged in pairs along the abdomen. They may probably be directly compared with the abdominal legs of Myriopods. Further study, however, of the homologies of these peculiar appendages, and especially a knowledge of the embryological development of Lepisma and Machilis, is needed before this interesting point can be definitely settled. The three many jointed anal stylets may, however, be directly compared with the similar appendages of Perla and Ephemera. The mode of insertion of the antennÆ of this family is much like that of the Myriopods, the front of the head being flattened, and concealing the base of the antennÆ, as in the Centipedes and Pauropus. Indeed, the head of any Thysanurous insect seen from above, bears a general resemblance in some of its features to that of the Centipede and its allies. So in a less degree does the head of the larvÆ of certain Neuroptera and Coleoptera. The eyes are compound, the single facets forming a sort of heap. The clypeus and labrum, or upper lip, is, in all the Thysanura, carried far down on the under side of the head, the clypeus being almost obsolete in the PoduridÆ, this being one of the most essential characters of that family. Indeed, it is somewhat singular that these and other important characteristics of this group have been almost entirely passed over by authors, who have consequently separated these insects from other groups on what appear to the writer as comparatively slight and inconsiderable characters. The mouth-parts of the LepismatidÆ (especially the thermophilous Lepisma, which we now describe) are most readily compared with those of the larva of Perla. The rather large, stout mandibles are concealed at their tips, under the upper lip, which moves freely up and down when the creature opens its mouth. The mandible is about one-third as broad as long, armed with three sharp teeth on the outer edge, and with a broad cutting edge within, and still further inwards a lot of straggling spinules. In all these particulars, the mandible of Lepisma is comparable with that of certain Coleoptera and Neuroptera. So also are the maxillÆ and labium, though we are not aware that any one has indicated how close the homology is. The accompanying figure (152) of the maxilla of a beetle may serve as an example of the maxilla of the Coleoptera, Orthoptera and Neuroptera. In these insects it consists almost invariably of three lobes, the outer being the palpus, the middle lobe the galea, and the innermost the lacinia; the latter undergoing the greatest modifications, forming a comb composed of spines and hairs varying greatly in relative size and length. How much the palpi vary in these groups of insects is well known. The galea sometimes forms a palpus-like appendage. Now these three lobes may be easily distinguished in the maxilla of Lepisma. The palpus instead of being directed forward, as in the insects mentioned above (in the pupa of Ephemera the maxilla is much like that of Lepisma), is inserted nearer the base than usual and thrown off at right angles to the maxilla, so that it is stretched out like a leg, and in moving about the insect uses its maxillÆ partly as supports for its head. They are very long and large, and five or six-jointed. The galea, or middle division, forms a simple lobe, while the lacinia has two large chitinous teeth on the inner edge, and internally four or five hairs arising from a thin edge.

The labium is much as in that of Perla, being broad and short, with a distinct median suture, indicating its former separation in embryonic life into a pair of appendages. The labial palpi are three-jointed, the joints being broad, and in life directed backwards instead of forwards as in the higher insects.

There are five American species of the genus Lepisma in the Museum of the Peabody Academy. Besides the common L. saccharina? there are four undescribed species; one found about out-houses and cellars, and the heat-loving form, perhaps an imported, species, found in a kitchen in Salem, and apparently allied to the L. thermophila Lucas, of houses in Brest, France; and lastly two allied forms, one from Key West, and another from Polvon, Western Nicaragua, collected by Mr. McNiel. The last three species are beautifully ornamented with finely spinulated hairs arranged in tufts on the head; while the sides of the body, and edges of the basal joints of the legs are fringed with them.

The interesting genus Nicoletia stands at the bottom of the group. It has the long, linear, scaleless body of Campodea, in the family below, but the head and its appendages are like Lepisma, the maxillary palpi being five-jointed, and the labial palpi four-jointed. The eyes are simple, arranged in a row of seven on each side of the head. The abdomen ends in three long and many jointed stylets, and there are the usual "false branchial feet" along each side of the abdomen. There are two European species which occur in greenhouses. No species have yet been found in America.

The next family of Thysanura is the CampodeÆ, comprising the two genera Campodea and Japyx. These insects are much smaller than the LepismidÆ, and in some respects are intermediate between that family and the PoduridÆ (including the SmynthuridÆ).

In this family the body is long and slender, and the segments much alike in size. There is a pair of spiracles on each thoracic ring. The mandibles are long and slender, ending in three or four teeth, and with the other appendages of the mouth are concealed within the head, "only the tips of the palpi (and of the maxillÆ when these are opened) projecting a very little beyond the rounded entire margin of the epistoma," according to Haliday. The maxillÆ are comb-shaped, due to the four slender, minutely ciliated spines placed within the outer tooth. The labium in Japyx is four-lobed and bears a small two-jointed palpus. The legs are five-jointed, the tarsi consisting of a single joint, ending in two large claws. The abdomen consists of ten segments, and in Campodea along each side is a series of minute, two-jointed appendages such as have been described in Machilis. These are wanting in Japyx. None of the species in this family have the body covered with scales. They are white, with a yellowish tinge.

The more complicated genus of the two is Japyx (Fig. 153, Japyx solifugus, found under stones in Southern Europe; a, the mouth from beneath, with the maxillÆ open; b, maxilla; d, mandible; c, outline of front of head seen from beneath, with the labial palpi in position) which, as remarked by the late Mr. Haliday (who has published an elaborate essay on this genus in the LinnÆan Transactions, vol. 24, 1864), resembles Forficula in the large forceps attached to its tail. An American species (J. Saussurii) lives in Mexico, and we look for its discovery in Texas.

Campodea (C. staphylinus Westw., Fig. 154, enlarged; a, mandible; b, maxilla), otherwise closely related, has more rudimentary mouth-parts, and the abdomen ends in two many jointed appendages.

Our common American species of Campodea (C. Americana) lives under stones in damp places. It is yellowish, about a sixth of an inch in length, is very agile in its movements, and would easily be mistaken for a very young Lithobius. A larger species and differing in having longer antennÆ, has been found by Mr. C. Cooke in Mammoth Cave, and has been described in the "American Naturalist" under the name of Campodea Cookei. Haliday has remarked that this family bears much resemblance to the Neuropterous larva of Perla (Fig. 155), as previously remarked by Gervais; and the many points of resemblance of this family and the LepismidÆ to the larval forms of some Neuroptera that are active in the pupa state (the Pseudoneuroptera of Erichson and other authors) are very striking. Campodea resembles the earliest larval form of ChloËon, as figured by Sir John Lubbock, even to the single jointed tarsus; and why these two Thysanurous families should be removed from the Neuroptera we are unable, at present, to understand, as to our mind they scarcely diverge from the Neuropterous type more than the Mallophaga, or biting lice, from the type of Hemiptera.

Haliday, remarking on the opinion of LinnÆus and Schrank, who referred Campodea to the old genus Podura, says with much truth, "it may be perhaps no unfair inference to draw, that the insect in question is in some measure intermediate between both," i. e., Podura and Lepisma. This is seen especially in the mouth-parts which are withdrawn into the head, and become very rudimentary, affording a gradual passage into the mouth-parts of the PoduridÆ, which we now describe.

The next group, the Podurelles of Nicolet, and Collembola of Lubbock, are considered by the latter, who has studied them with far more care than any one else, as "less closely allied" to the LepismidÆ "than has hitherto been supposed." He says "the presence of tracheÆ, the structure of the mouth and the abdominal appendage; all indicate a wide distinction between the LepismidÆ and the PoduridÆ. We must, indeed, in my opinion, separate them entirely from one another; and I would venture to propose for the group comprised in the old genus Podura, the term Collembola, as indicating the existence of a projection, or mammilla, enabling the creature to attach or glue itself to the body on which it stands." Then without expressing his views as to the position and affinities of the LepismidÆ, he remarks "as the upshot of all this, then, while the Collembola are clearly more nearly allied to the Insecta than to the Crustacea or Arachnida, we cannot, I think, regard them as Orthoptera or Neuroptera, or even as true insects. That is to say, the Coleoptera, Orthoptera, Neuroptera, Lepidoptera, etc., are in my opinion, more nearly allied to one another than they are to the PoduridÆ or SmynthuridÆ. On the other hand, we certainly cannot regard the Collembola as a group equivalent in value to the Insecta. If, then, we attempt to map out the Articulata, we must, I think, regard the Crustacea and Insecta as continents, the Myriopoda and Collembola as islands—of less importance, but still detached. Or, if we represent the divisions of the Articulata like the branching of a tree, we must picture the Collembola as a separate branch, though a small one, and much more closely connected with the Insecta than with the Crustacea or the Arachnida." Lamarck regarded them as more nearly allied to the Crustacea than Insecta. Gervais, also, in the "Histoire Naturelle des Insectes: AptÈres," indicates a considerable diversity existing between the LepismidÆ and PoduridÆ, though they are placed next to each other. Somewhat similar views have been expressed by so high an authority as Professor Dana, who, in the "American Journal of Science" (vol. 37, Jan., 1864), proposed a classification of insects based on the principle of cephalization, and divided the Hexapodous insects into three groups: the first (Ptero-prosthenics, or Ctenopters) comprising the Hymenoptera, Diptera, Aphaniptera (fleas), Lepidoptera, Homoptera, Trichoptera and Neuroptera; the second group (Ptero-metasthenics, or Elytropters) comprising the Coleoptera, Hemiptera and Orthoptera; while the Thysanura compose the third group. Lubbock has given us a convenient historical view of the opinions of different authors regarding the classification of these insects, which we find useful. Nicolet, the naturalist who, previous to Lubbock, has given us the most correct and complete account of the Thysanura, regarded them as an order, equivalent to the Coleoptera or Diptera, for example. In this he followed Latreille, who established the order in 1796. The AbbÉ Bourlet adopted the same view. On the other hand Burmeister placed the Thysanura as a separate tribe between the Mallophaga (Bird Lice) and Orthoptera, and Gerstaecker placed them among the Orthoptera. Fabricius and Blainville put them with the Neuroptera, and the writer, in his "Guide to the Study of Insects," and previously in 1863, ignorant of the views of the two last named authors, considered the Thysanura as degraded Neuroptera, and noticed their resemblance to the larvÆ of Perla, Ephemera, and other Neuroptera, such as Rhaphidia and Panorpa, regarding them as standing "in the same relation to the rest of the Neuroptera [in the LinnÆan sense], as the flea does to the rest of the Diptera, or the lice and Thrips to the higher Hemiptera."

After having studied the Thysanura enough to recognize the great difficulty of deciding as to their affinities and rank, the writer does not feel prepared to go so far as Dana and Lubbock, for reasons that will be suggested in the following brief account of the more general points in their structure, reserving for another occasion a final expression of his views as to their classification.

The PoduridÆ, so well known by name, as affording the scales used by microscopists as test objects, are common under stones and wet chips, or in damp places, cellars, mushrooms and about manure heaps. They need moisture, and consequently shade. They abound most in spring and autumn, laying their eggs at both seasons, though most commonly in the spring. During a mild December, they may be found in abundance under sticks and stones, even in situations so far north as Salem, Mass.

The body of the Poduras is rather short and thick, most so in Smynthurus (Fig. 156), and becoming long and slender in Tomocerus and Isotoma. The segments are inclined to be of unequal size, the prothoracic ring sometimes becoming almost obsolete, and some of the abdominal rings are much smaller than others; while in Lipura and Anura, the lowest forms of the group, the segments are all much alike in size.

The head is in form much like that of certain larvÆ of Neuroptera and of Forficula, an Orthopterous insect. The basal half of the head is marked off from the eye-bearing piece (epicranium) by a V-shaped suture[10] (Fig. 157, head of Degeeria; compare also the head of the larva of Forficula, Fig. 158, in which the suture is the same), and the insertion of the antennÆ is removed far down the front, near the mouth, the clypeus being very short; this piece, so large and prominent in the higher insects, is not distinctly separated by suture from the surrounding parts of the head, thus affording one of the best distinctive characters of the PoduridÆ. The eyes are situated on top of the head just behind the antennÆ, and are simple, consisting of a group of from five to eight or ten united into a mass in Smynthurus, but separated in the PoduridÆ (see Fig. 176, e, eye of Anurida). The antennÆ are usually four-jointed, and vary in length in the different genera.

The mouth-parts are very difficult to make out, but by soaking the insect in potash for twenty-four hours, thus rendering the body transparent, they can be satisfactorily observed. They are constructed on the same general type as the mouth-parts of the Neuroptera, Orthoptera and Coleoptera, and except in being degraded, and with certain parts obsolete, they do not essentially differ.[11] On observing the living Podura, the mouth seems a simple ring, with a minute labrum and groups of hairs and spinules, which the observer, partly by guess-work, can identify as jaws and maxillÆ, and labium. But in studying the parts rendered transparent, we can identify the different appendages. Figure 159 shows the common Tomocerus plumbeus greatly enlarged (Fig. 160, seen from above), and as the mouth-parts of the whole group of Poduras are remarkably constant, a description of one genus will suffice for all. The labrum, or upper lip, is separated by a deep suture from the clypeus, and is trapezoidal in form. The mandibles and maxillÆ are long and slender, and buried in the head, with the tips capable of being extended out from the ring surrounding the mouth for a very short distance. The mandibles (md, Fig. 159) are like those of the Neuroptera, Orthoptera and Coleoptera in their general form, the tip ending in from three to six teeth (three on one mandible and six on the other), while below, is a rough, denticulated molar surface, where the food seized by the terminal teeth is triturated and prepared to be swallowed. Just behind the mandibles are the maxillÆ, which are trilobate at the end, as in the three orders of insects above named. The outer lobe, or palpus, is a minute membranous tubercle ending in a hair (Fig. 161, mp), while the middle lobe, or galea, is nearly obsolete, though I think I have seen it in Smynthurus, where it forms a lobe on the outside of the lacinia. The lacinia, or inner lobe (Fig. 161, lc; 162, the same enlarged), in Tomocerus consists of two bundles of spinules, one broad like a ruffle, and the other slender, pencil-like, ending in an inner row of spines, like the spinules on the lacinia of the Japyx and Campodea and, more remotely, the laciniÆ of the three sub-orders of insects above referred to. There is also a horny, prominent, three-toothed portion (Fig. 161, g). These homologies have never been made before, so far as the writer is aware, but they seem natural, and suggested by a careful examination and comparison with the above-mentioned mandibulate insects.

The spring consists of a pair of three-jointed appendages, with the basal joints soldered together early in embryonic life, while the other two joints are free, forming a fork. It is longest in Smynthurus and Degeeria, and shortest in Achorutes (Fig. 172, b), where it forms a simple, forked tubercle; and is obsolete in Lipura and Anura, its place being indicated by an oval scar. The third joint varies in form, being hairy, serrate and knife-like in form, as in Tomocerus (Fig. 159, a), or minute, with a supplementary tooth, as in Achorutes (Fig. 172, c). This spring is in part homologous with the ovipositor of the higher insects, which originally consists of three pairs of tubercles, each pair arising apparently from the seventh, eighth, and ninth (the latter the penultimate) segments of the abdomen in the Hymenoptera. The spring of the Podura seems to be the homologue of the third pair of these tubercles, and is inserted on the penultimate segment. This comparison I have been able to make from a study of the embryology of Isotoma.

Another organ, and one which, so far as I am aware, has been overlooked by previous observers, I am disposed to consider as possibly an ovipositor. In the genus Achorutes, it may be found in the segment just before the spring-bearing segment, and situated on the median line of the body. It consists (Fig. 163) of two squarish valves, from between which projects a pair of minute tubercles, or blades, with four rounded teeth on the under side. This pair of infinitesimal saws reminds one of the blades of the saw-fly, and I am at a loss what their use can be unless to cut and pierce so as to scoop out a shallow place in which to deposit an egg. It is homologous in situation with the middle pair of blades which composes the ovipositor of higher insects, and if it should prove to be used by the creature in laying its eggs, we should then have, with the spring, an additional point of resemblance to the Neuroptera and higher insects, and instead of this spring being an important differential character, separating the Thysanura from other insects, it binds them still closer, though still differing greatly in representing only a part of the ovipositor of the higher insects. (This is a catch for holding the spring in place.)

But all the Poduras differ from other insects in possessing a remarkable organ situated on the basal segment of the abdomen. It is a small tubercle, with chitinous walls, forming two valves from between which is forced out a fleshy sucker, or, as in Smynthurus, a pair of long tubes, which are capable of being darted out on each side of the body, enabling the insect to attach itself to smooth surfaces, and rest in an inverted position.

The eggs are laid few in number, either singly or several together, on the under side of stones, chips or, as in the case of Isotoma Walkerii, under the bark of trees. They are round, transparent. The development of the embryo of Isotoma in general accords with that of the PhryganeidÆ and suggests on embryological grounds the near relationship of the Thysanura to the Neuroptera.

The earliest stage observed was at the time of the appearance of the primitive band (Fig. 164, a, b, folding of the primitive band; c, the dotted line crosses the primitive band, and terminates in a large yolk granule) which surrounds the egg as in the Caddis flies. Soon after, the primitive segments appear (Fig. 165; 1, antennÆ; 2, mandibles; 3, maxillÆ; the labium was not seen; 5-7, legs; c, yolk surrounded by the primitive band) and seem to originate just as in the Caddis flies. Figure 166 is a front view of the embryo shortly before it is hatched; figure 167, side view of the same, the figures as in Fig. 165; sp, spring; l, labrum. The labrum or upper lip, and the clypeus are large and as distinct as in the embryos of other insects, a fact to which we shall allude again. The large three-jointed spring is now well developed, and the inference is drawn that it represents a pair of true abdominal legs. The embryo when about to hatch throws off the egg-shell and amnion in a few seconds. The larva is perfectly white and is very active in its movements, running over the damp, inner surface of the bark. It is a little over a hundredth of an inch in length, and differs from the adult in being shorter and thicker, with the spring very short and stout. In fact the larva assumes the form of the lower genera of the family, such as Achorutes and Lipura, the adult more closely resembling Degeeria. The larva after its first moult retains its early clumsy form, and is still white. After a second moult it becomes purplish, and much more slender, as in the adult. The eggs are laid and the young hatched apparently within a period of from six to ten days.

Returning to the stage indicated by figures 166 and 167, I am induced to quote some remarks published in the Memoirs of the Peabody Academy of Science, No. 2, p. 18, which seem to support the view that these insects are offshoots from the Neuroptera.

"The front of the head is so entirely different from what it is in the adult, that certain points demand our attention. It is evident that at this period the development of the insect has gone on in all important particulars much as in other insects, especially the Neuropterous Mystacides as described by Zaddach. The head is longer vertically than horizontally, the frontal, or clypeal region is broad, and greater in extent than the epicranio-occipital region. The antennÆ are inserted high up on the head, next the ocelli, falling down over the clypeal region. The clypeus, however, is merged with the epicranium, and the usual suture between them does not appear distinctly in after life, though its place is seen in figure 167 to be indicated by a slight indentation. The labrum is distinctly defined by a well marked suture, and forms a squarish, knob-like protuberance, and in size is quite large compared to the clypeus. From this time begins the process of degradation, when the insect assumes its Thysanurous characters, which consist in an approach to the form of the Myriopodous head, the front, or clypeal region being reduced to a minimum, and the antennÆ and eyes brought in closer proximity to the mouth than in any other insects."

Sir John Lubbock has given us an admirable account of the internal anatomy of these little creatures, his elaborate and patient dissections filling a great gap in our knowledge of their internal structure. The space at our disposal only permits us to speak briefly of the respiratory system. Lubbock found a simple system of tracheÆ in Smynthurus which opens by "two spiracles in the head, opposite the insertion of the antennÆ," i. e., on the back of the head. (Von Olfers says that they open on the prothorax.) Nicolet and Olfers claim to have found tracheÆ in several lower genera (Orchesella, Tomocerus, and Achorutes and allied genera), but Lubbock was unable to detect them, and I may add that I have not yet been able after careful search to find them either in living specimens, or those rendered transparent by potash.

Having given a hasty sketch of the external aspect of the Poduras, I extract from Lubbock's work a synopsis of the families and genera for the convenience of the student, adding the names of known American species, or indications of undescribed native forms.

SmynthuridÆ.—Body globular or ovoid; thorax and abdomen forming one mass; head vertical or inclined; antennÆ of four or eight segments. Eyes eight on each side, on the top of the head. Legs long and slender. Saltatory appendage with a supplementary segment.

Smynthurus. AntennÆ four-jointed, bent at the insertion of the fourth, which is nearly as long as the other three, and appears to consist of many small segments. No conspicuous dorsal tubercles. (In this country Fitch has described five species: S. arvalis, elegans, hortensis, NovÆboracensis, and signifer. Figure 156 represents a species found in Maine.)

Dicyrtoma. AntennÆ eight-jointed, five before, three after the bend. Two dorsal tubercles on the abdomen.

Papirius.[12] AntennÆ four-jointed, without a well-marked elbow, and with a short terminal segment offering the appearance of being many-jointed.

PoduridÆ.—This family comprises those species of the old genus Podura, in which the mouth has mandibles [also maxillÆ and a labium], and the body is elongated, with a more or less developed saltatory appendage at the posterior extremity.

Orchesella. Segments of the body unequal in size, more or less thickly clothed with clubbed hairs. AntennÆ long, six-jointed. Eyes six in number on each side, arranged in the form of an S. (One or two beautiful species live about Salem.)

Degeeria. Segments of the body unequal in size, more or less thickly clothed by clubbed hairs. AntennÆ longer than the head and thorax, filiform, four-jointed. Eyes eight in number on each side of the head. (Two species, Degeeria decem-fasciata, Pl. 10, Figs. 2, 3, and D. purpurascens, Figs. 4, 5, are figured in the "Guide to the Study of Insects." Figure 168 represents a species found in Salem, Mass., closely allied to the European D. nivalis. Five species are already known in New England.)

Seira. Body covered with scales. AntennÆ four-jointed; terminal segment not ringed. Eyes on a dark patch. Thorax not projecting over the head. Abdominal segments unequal.

Templetonia. Segments of the body subequal, clothed by clubbed hairs, and provided with scales. AntennÆ longer than the head and thorax, five-jointed, with a small basal segment, and with the terminal portion ringed.

Isotoma. Four anterior abdominal segments subequal, two posterior ones small; body clothed with simple hairs and without scales. AntennÆ four-jointed, longer than the head; segments subequal. Eyes seven in number on each side, arranged in the form of an S. (Three species are found in Massachusetts, one of which (I. plumbea) is figured on Pl. 10, Figs. 6, 7, of the "Guide to the Study of Insects," third edition.)

Tomocerus. Abdominal segments unequal, with simple hairs and scales. AntennÆ very long, four-jointed, the two terminal segments ringed. Eyes seven in number on each side. (The European T. plumbea, Podura plumbea of authors, is our species, and is common. Fig. 160, greatly enlarged, copied from Templeton; Fig. 159, side view, see also Fig. 161, where the mouth-parts are greatly enlarged, the lettering being the same, md, mandibles; mx, maxillÆ; mp, maxillary palpus; lb, labium; lp, labial palpus; lc, lacinia; g, portion ending in three teeth; l, lobe of labium; sp, ventral sucking disk; the dotted line's passing through the body represent the course of the intestine; b, end of tibia, showing the tarsus, with the claw, and two accessory spines; a, third joint of the spring. Fig. 162, lacinia of maxilla greatly enlarged. Fig. 169, different forms of scales, showing the great variation in size and form, the narrow ones running into a linear form, becoming hairs. The markings are also seen to vary, showing, their unreliable character as test objects, unless a single scale is kept for use.)

Lepidocyrtus. Abdominal segment unequal, with simple hairs and scales. AntennÆ long, four-jointed. Eyes eight in number on each side. (Fig. 170, L. albinos, an European species, from Hardwicke's "Science Gossip." Fig. 171, a scale. Two species live in New England.)

Podura. Abdominal segments subequal. Hairs simple, no scales. AntennÆ four-jointed, shorter than the head. Eyes eight in number on each side. Saltatory appendage of moderate length.

Achorutes. Abdominal segments subequal. AntennÆ short, four-jointed. Eyes eight in number on each side. Saltatory appendage quite short.

Figure 172 represents a species of this genus very abundant under the bark of trees, etc., in New England. It is of a blackish lead color; a, end of tibia bearing a tenant hair, with the tarsal joint and large claw; b, spring; c, the third joint of the spring, with the little spine at the base; figure 163, the supposed ovipositor; a, the two blades spread apart; b, side view. The mouth-parts in this genus are much as in Tomocerus, the maxillÆ ending in a lacinia and palpus.

The three remaining genera, Lipura, Anurida and Anura, are placed in the "family" LipuridÆ, which have no spring. Lubbock remarks that "this family contains as yet only two[13] genera, Lipura (Burmeister), in which the mouth is composed of the same parts as those in the preceding genera, and Anura (Gervais), in which the mandibles and maxillÆ disappear." Our common white Lipura is the European L. fimetaria Linn. (Fig. 173, copied from Lubbock). The site of the spring is indicated by an oval scar.

Figure 174 represents Anurida maritima found under stones between tide marks at Nantucket. It is regarded the same as the European species by Lubbock, to whom I had sent specimens for comparison. This genus differs in the form of the head from Lipura and also wants the terminal upcurved spines, while the antennÆ are much more pointed. The legs (Fig. 175) end in a large, long, curved claw. On examining specimens soaked in potash, I have found that the mouth-parts of this species (Fig. 176,) md, mandibles; mx, maxillÆ; e, eyes, and a singular accessory group of small cells, are like those of Achorutes, as previously noticed by LaboulbÈne. The mandibles, like those of other Poduras, end in from three to six teeth, and have a broad, many-toothed molar surface below. The maxillÆ; end in a tridentate lacinia as usual, though the palpi and galea I have not yet studied.

The genus Anura may be readily recognized by the mouth ending in an acutely conical beak, with its end quite free from the head and hanging down beneath it. The body is short and broad, much tuberculated, while the antennÆ are short and pointed, and the legs are much shorter than in Lipura, not reaching more than a third of their length beyond the body. Our common form occurs under the bark of trees.

For the reason that I can find no valid characters for separating these three genera as a family from the other Poduras, I am inclined to think that they form, by the absence of the spring, only a subdivision (perhaps a subfamily) of the PoduridÆ.

The best way to collect Poduras is, on turning up the stick or stone on the under side of which they live, to place a vial over them, allowing them to leap into it; they may be incited to leap by pushing a needle under the vial. They may also be collected by a bottle with a sponge saturated with ether or chloroform. They may be kept alive for weeks by keeping moist slips of blotting paper in the vial. In this way I have kept specimens of Degeeria, Tomocerus and Orchesella, from the middle of December till late in January. During this time they occasionally moulted, and Tomocerus plumbeus, after shedding its skin, ate it within a few hours. Poduras feed ordinarily on vegetable matter, such as dead leaves and growing cryptogamic vegetation. These little creatures can be easily preserved in a mixture of alcohol and glycerine, or pure alcohol, though without the glycerine the colors fade.

We have entered more fully in this chapter into the details of structure than heretofore, too much so, perhaps, for the patience of our readers. But the study of the Poduras possesses the liveliest interest, since these lowest of all the six-footed insects may have been among the earliest land animals, and hence to them we may look with more or less success for the primitive, ancestral forms of insect life.