Myriapoda

“ In this family the principal generic characters are founded upon the number of the segments of the body, the shape of the head, the number and form of the spiracles, the absence or presence of eyes, and the form of the terminal segment and its appendages. In some cases the number of joints of the antennæ seems to be a constant generic sub-character. In the large genus Scolopendra—the Titans of the Myriapoda—the principal specific characters are founded upon, first, the number of segments to the antennæ ”

“ Originally the body is composed of a congeries of cells, segment after segment being added, exactly in the same manner as in the case of the Annelida, with which in structure they closely agree, being adapted, however, to live on land. The Annelida seem then to be the ancestors of the Myriapoda, Insects, and Spiders, the Myriapoda retaining much of the Annelid structure through life, whereas the Insect is an Annelid or Myriapod only when in a larval or undeveloped condition. That the development of the different kinds of insects has been gradual. ”

“ HABITS–CLASSIFICATION–STRUCTURE–CHILOGNATHA–CHILOPODA–SCHIZOTARSIA–SYMPHYLA–PAUROPODA–EMBRYOLOGY–PALAEONTOLOGY.
Tracheata with separated head and numerous, fairly similar segments. They have one pair of antennae, two or three pairs of mouth appendages, and numerous pairs of legs.
The Myriapoda are a class of animals which are widely distributed, and are represented in almost every part of the globe. Heat and cold alike seem to offer favourable conditions for their existence, and they flourish both in the most fertile and the most barren countries. ”

“ Species mihi ignota.
Variegated with ferruginous; head large, subquadrate, polished, elevated, and thickened at its posterior margin; antennæ short, pubescent; ocelli on each side 23; labium polished, with scattered hairs; dental lamina lunate, anterior external angles elongate, profoundly emarginate; denticules 14 acute, black; dorsal scuta complanate rugose, their margins elevated; feet bare, with small articular spines. Species unknown to me.
L. planus, Newport, Linn. Trans, xix, p. 366; Catalogue of British Museum (Myriapoda) , p. 18.
"⁠"⁠P. Gervais, Apt. iv, p. 236; et Tabl. ”

“ MYRIAPODA (Gr. for “ many-legged ”) , arthropod animals of which centipedes and millipedes are familiar examples. Linnaeus included them in his Insecta Aptera together with Crustacea and Arachnida; in 1796 P. A. Latreille designated them as Myriopoda, making of them, along with the Crustacean Oniscus, one of the seven orders into which he divided the Aptera of Linnaeus. Later on J. C. Savigny, by study of the mouth-parts, clearly distinguished them from Insects and Crustacea. In 1814 W. E. Leach defined them and divided them into Centipedes and Millipedes. ”

“ Before leaving for Madeira, Metchnikoff had obtained a scientific mission and a subsidy from the Society of Natural Science Lovers of Moscow, and felt it a moral obligation to obtain some results. The scantiness of the marine fauna was a bitter disappointment; he had to fall back upon what little he found, and embarked on the study, hitherto unknown, of the embryology of Myriapoda. ”

“ Such a discovery renders all speculation as to the origin of true insects premature, because we may feel sure that all the other orders of insects, except perhaps hymenoptera and lepidoptera, were contemporaneous with the highly specialised beetles.
The less highly organised terrestrial arthropoda—the Arachnida and Myriapoda—are, as might be expected, much more ancient. A fossil spider has been found in the Carboniferous, and scorpions in the Upper Silurian rocks of Scotland, Sweden, and the United States. Myriapoda have been found abundantly in the Carboniferous and Devonian formations ”

“ The Schizotarsia, the third Order, also have seven pairs of legs when hatched.
The legs make their appearance not one by one but in batches (in Julus terrestris in batches of five) . The addition of legs and segments to the body takes place, not at the end of the body, but between the end segment and the penultimate.
This is a short sketch of the gradual development of the Myriapoda from the ovum to the fully-grown animal. ”

“ They appear to belong to the mouth-parts. The internal anatomy will be found to be, if examined, much like that of insects and can be studied from the account of the anatomy of the water-scavenger beetle and butterfly larva. Compare the Myriapods with the Hexapods or true insects. What are the points of resemblance? what are the points of difference?
The Myriapoda are land-animals breathing by means of tracheæ like the insects. In them the body-segments [Pg 227] are nearly uniform in character with the exception of the head, which, as in the insects, bears the mouth-parts and antennæ. ”

“ Whilst traversing some oases where the Russians were making experiments in artificial forestry, he had the pleasant surprise of finding some Myriapoda (Geophilus) bearing a number of eggs. The history of the development of those creatures was still unknown—a notable lacuna in embryology. Delighted at the idea of filling it, Metchnikoff did not hesitate to undertake a long and difficult extra journey and repaired to Astrakhan, taking with him his precious material, in order to fetch the necessary apparatus for his researches. ”

“ Pliny tells us of a marine Scolopendra, but this was most probably a species of marine worm.
Linnaeus included Myriapods among the Insects; and the writers after him till the beginning of this century classed them with all sorts of Insects, with Spiders, Scorpions, and even among Serpents. It was Leach who first raised them to the importance of a separate class, and Latreille first gave them the name of Myriapoda, which they have retained ever since.
Myriapods are terrestrial animals, crawling or creeping on the ground or on logs of wood, or even under the bark of trees. ”

“ The resemblance between the Chilopoda and the Diplopoda is principally superficial and due to the elongation and vermiform shape of the body, which in both is composed of a number of similar or subsimilar somites not differentiated as are those of Insecta, existing Arachnida and most Crustacea, into series or “tagmata” of varying function. Until 1893 no one doubted the correctness of the assumption that the Chilopoda and Diplopoda were orders of a class Myriapoda of the same systematic status as the Arachnida or Hexapoda. ”

“ In this species the superior spine of the lateral anal appendages is very minute, and occasionally present only on one side. The color varies from milk-white to a dark reddish orange. The lighter shades are found in those individuals which have recently shed their skins. The color given in the diagnosis may be considered as that which characterizes the species, being the one to which it finally attains. ”

“ The antennæ are formed according to the type of the Diplopoda, with seven joints. The body is composed of numerous segments. The scuta may be prolonged laterally into laminæ, but afford protection only to the back and flanks; the central part of the abdomen is not covered by a firm, resistant shell. The feet are hidden beneath the broad body. The male genitalia are placed in the seventh segment. In the classification of the families and genera I have followed Mr. Brandt, [26] his arrangement, as far as the two species I have seen enable me to judge, being founded on natural characters. ”

“ Its anterior face is marked with two small punctiform impressions. The lower border is not very strongly emarginate, and is set with a fringe of short thick hairs. The antennæ are mostly dark-colored, scarcely at all clavate, and coarsely pubescent. The feet are rough, with closely set, stiff hairs. The anal scutum is prolonged posteriorly, so as to come almost to a blunt point. The appendages in the male are short and thick. Their terminal spine is slightly curved at its base, thence is nearly straight, save at its distal extremity, where it is abruptly curved, becoming nearly horizontal. ”

“ Now, their method of development is similar to that of the Vermes, hence the reason of their being placed next above them. When a spider, or insect, or crustacean leaves the egg, its body has its maximum number of segments, and development takes place by the coalescence and disappearance of some of these. The embryonic myriapod, on the contrary, has its minimum number of segments, and develops by their increase. So that whilst the adult insect has generally fewer, never more segments than the young, the adult myriapod may have eight times as many, and never fewer than its young. [3] ”

“ The body in the Chilopoda is composed of segments, whose number varies from sixteen to several hundred. Each segment is furnished with a single pair of legs. There might seem to be an exception to this in the Cermatiidæ, but close examination shows that in them the fact of there being but one scutum to two segments is the cause of the apparent anomaly. In all the other families there is a scutum and sternum to each segment. These external bones, so to speak, are connected by a tough membrane, which forms the only protection to the sides. ”

“ P. erythropygus, Brandt, Recueil, p. 134.
⁠"⁠ Gervais, Suit, a Buffon, Apteres, vol. iv, p. 106; Exped. L'Amer. du Sud (Castelneau) , Myriapoda, p. 6.
⁠"⁠ Saussure, Mem. Soc. Nat. Hist. Geneva, vol. xv, p. 296.
P. Carolinensis, Saussure, Mem. Soc. Nat. Hist. Geneva, vol. xv, p. 295.
⁠"⁠ Gervais, Exped. L'Amer. du Sud (Castelneau) , Myriap., p. 14.
The general color of this elegant species is an olive-chestnut; in some individuals the olive overpowering the other tint, and approaching Sometimes to a slate color; in others the chestnut predominating. ”

“ Newport and others have not allowed these characters the weight that they deserve. Mr. Gray does not even allow them generic force, if his classification (Cyclop. Anat. and Physiol., art. Myriap.) is to be trusted. Or was he entirely ignorant of their existence! Newport gives to them a family significance.
The different structure of the mouth, and the consequent different food and habits of living, although not sufficient to stand in competition with the characters separating the Chilopoda and Diplopoda, are still of higher import than any other differences in the latter order. ”

“ The Diplopods depend upon the vegetable kingdom for their sustenance. The body is much more rigid than in the Chilopods, from the close conjunction, or often imbrication, of the segments, and the inflexibility of the segments themselves, caused by the density and thickness of the scuta aud sterna and the absence of lateral membranes. For this reason the Diplopoda possess but little or none of that power of raising and twisting the body, which is so annoying to the collector of tropical Scolopendra. ”

“ The vertex furrow is strongly pronounced. The anterior surface of the head has a pair of almost obsolete punctiform impressions, and is scarcely emarginate. The antennæ are coarsely pubescent, and not clavate. The first scutum frequently has an orange spot on its anterior margin. The last scutum has its posterior portion very broad, thin, and of an orange hue. The lateral laminæ are larger than in P. hispidipes; and their edges, though thickened, are not so much so as in that species. They are bright both on their Upper and under surfaces. ”

“ Light yellow; body very depressed, rather broad, anteriorly slightly narrowed; head large; cephalic segment subtriangular; antennæ short, moniliform, posteriorly slightly depressed, thick, anteriorly cylindrical, not acuminate, with a few soft, very short hairs; labium short, broad, anteriorly obsoletely bidentate, impressed with a slightly pronounced median sulcus; mandibles thick; scuta very short, without sutures, but with sometimes an obscure median line; sterna very short, each with a single submedian ovate depression, most conspicuous on the anterior portion of the body ”

“ As a general rule, the fewer the segments the higher the organization. Each perfected segment is formed from two subsegments, either by their coalescence and mutual growth, or by the atrophy of one and the hypertrophy of the other. The dorsal and ventral portions of the subsegments are each formed originally from four pieces. The two central unite very early in the embryo, and completely fusing form the primitive scuta and sterna, with which the outer pieces, the episcuta and episterna, unite sooner or later. ”

“ The posterior legs furnish the best criteria in the distinguishing of species. Most species have peculiarities either in the shape or relative size of the joints, or in the number or arrangement of spines on them. In order to show the amount of constancy that these characters possess, I have drawn up a series of tables, which may aid in establishing their value. The color, I think, is not to be depended upon, although Mr. Newport seems to attach much importance to it. In the preservation of specimens it is very liable to be altered or destroyed ”

“ The anterior scuta are tuberculate, the posterior merely roughened. Each has a more or less obsolete transverse groove extending all across the lateral laminæ. The latter are very long and narrow; they are placed very close together, and are often bent slightly backwards. Their external margin is somewhat oblique, and is furnished in all except, perhaps, the most anterior, with a pore. The small feet are entirely concealed beneath the broad body. ”

“ Surface markings more generally characterize small groups than individual species, yet are sometimes available even in closely allied forms. The possession of a mucro characterizes groups; whilst its size and its shape are often specific. As in all the other Diplopoda each species has a peculiar and persistent form of the Genitalia, more marked in the male than in the female. Indeed a certain type of arrangement seems in this group to characterize a genus.
Genus IULUS.
Scutum primum magnum, lateribus in femina nonnihil productis. ”