Cla.s.s VI. The _Insecta_ (Insects).
That branch of zoology which treats of insects is known as entomology.
The _Insecta_ have been variously subdivided by different scientific writers, but the following subdivision has much in it to commend it, and will suffice as an outline for the guidance of the advanced student.
CLa.s.s VI. INSECTA (INSECTS PROPER)
HETEROMETABOLA
For the most part undergoing only a partial metamorphosis in the development from the egg to the imago.
ORDERS
1. _Thysanura._ Suborders: _Collembola_ (Podura, Springtails).
_Symphyla_ (Scolopendrella).
_Cinura_ (Bristletails, etc.).
2. _Dermatoptera_ (Earwigs).
3. _Pseudoneuroptera._ Suborders: _Mallophaga_ (Bird-lice).
_Platyptera_ (Stone-flies, Termites, etc.).
_Odonata_ (Dragon-flies, etc.).
_Ephemerina_ (May-flies, etc.).
4. _Neuroptera_ (Corydalis, Ant-lion, Caddis-flies, etc.).
5. Orthoptera (c.o.c.kroach, Mantis, Mole-cricket, Gra.s.shopper, Katydid, etc.).
6. _Hemiptera._ Suborders: _Parasita_ (Lice).
_Sternorhyncha_ (Aphids, Mealy Bugs, etc.).
_h.o.m.optera_ (Cicada, Tree-hoppers, etc.).
_Heteroptera_ (Ranatra, Belostoma, Water-spiders, Squash-bugs, Bedbugs, etc.).
7. _Coleoptera._ Suborders: _Cryptotetramera_ (Lady-birds, etc.).
_Cryptopentamera_ (Leaf-beetles, Longhorns, Weevils, etc.).
_Heteromera_ (Blister-beetles, Meal-beetles, etc.).
_Pentamera_ (Fire-flies, Skipjacks, June-bugs, Dung-beetles, Stag-beetles, Rove-beetles, Tiger-beetles, etc.).
METABOLA
Undergoing for the most part a complete metamorphosis from egg, through larva and pupa, to imago.
ORDERS
8. _Aphaniptera_ (Fleas).
9. _Diptera._ Suborders: _Orthorhapha_ (Hessian Flies, Buffalo-gnats, Mosquitos, Crane-flies, Horse-flies).
_Cyclorhapha_ (Syrphus, Bot-flies, Tsetse, House-flies, etc.).
10. _Lepidoptera._ Suborders: _Rhopalocera_ (b.u.t.terflies).
_Heterocera_ (Moths).
11. _Hymenoptera._ Suborders: _Terebrantia_ (Saw-flies, Gall-wasps, Ichneumon-flies, etc.).
_Aculeata_ (Ants, Cuckoo-flies, Digger-wasps, True Wasps, Bees).
It will be seen by glancing at the foregoing table that the b.u.t.terflies and moths are included as suborders in the tenth group of the list, to which is applied the name _Lepidoptera_. This word, like most other scientific words, is derived from the Greek, and is compounded of the noun (_?ep??_), which signifies a _scale_, and the noun (_pte???_), which signifies a _wing_. The b.u.t.terflies and moths together const.i.tute the order of scale-winged insects. The appropriateness of this name will no doubt be at once recognized by every reader, who, having perhaps unintentionally rubbed off some of the minute scales which clothe the wings of a b.u.t.terfly, has taken the trouble to examine them under a microscope, or who has attentively read what has been said upon this subject in the first chapter of this book. By referring again to the cla.s.sification which has been given, it will be noted that the last four orders in the list agree in that the creatures included within them undergo for the most part what is known as a complete metamorphosis; that is to say, they pa.s.s through four successive stages of development, existing first as eggs, then as worm-like larvae, or caterpillars, then as pupae, and finally as perfect, fully developed insects, gifted for the most part with the power of flight, and capable of reproducing their kind. All of this has been to some extent already elucidated in the first chapter of the present volume, but it may be well to remind the reader of these facts at this point.
[Ill.u.s.tration FIG. 76.--Antennae of b.u.t.terflies.]
A question which is frequently asked by those who are not familiar with the subject relates to the manner in which it is possible to distinguish between moths and b.u.t.terflies. A partial answer can be made in the light of the habits of the two cla.s.ses of lepidoptera. b.u.t.terflies are diurnal in their habits, flying between sunrise and dusk, and very rarely taking the wing at night. This habit is so universal that these insects are frequently called by entomologists "the diurnal lepidoptera," or are simply spoken of as "diurnals." It is, however, true that many species of moths are also diurnal in their habits, though the great majority of them are nocturnal, or crepuscular, that is, flying at the dusk of the evening, or in the twilight of the early morning. Upon the basis of mere habit, then, we are able only to obtain a partial clue to the distinction between the two suborders. A more definite distinction is based upon structure, and specifically upon the structure of the antennae. b.u.t.terflies have long, thread-like antennae, provided with a swelling at the extremity, giving them a somewhat club-shaped appearance (Fig. 76). This form of antennae is very unusual among the moths, and only occurs in a few rare genera, found in tropical countries, which seem to represent connecting-links between the b.u.t.terflies and the moths. All the true moths which are found within the limits of the United States and Canada have antennae which are not club-shaped, but are of various other forms. Some moths have thread-like antennae tapering to a fine point; others have feather-shaped antennae; others still have antennae which are prismatic in form, and provided with a little hook, or spur, at the end; and there are many modifications and variations of these forms. The club-shaped form of the antennae of b.u.t.terflies has led naturalists to call them _Rhopalocera_, as has been already explained in speaking of this subject on page 17. Moths are called _Heterocera_. The word _Heterocera_ is compounded of the Greek word (_pte???_), meaning _other_, and the Greek word (_?e?a?_), meaning a _horn_. They are lepidoptera which have antennae which are _other than club-shaped_.
Besides the distinctions which exist in the matter of the form of the antennae, there are distinctions in the veins of the wings, and in the manner of carrying them when at rest or in flight, which are quite characteristic of the two groups; but all of these things the attentive student will quickly learn for himself by observation.
[Ill.u.s.tration FIG. 77.--Antennae of moths.]
_Scientific Arrangement._--Having thus cast a pa.s.sing glance at the differences which exist between moths and b.u.t.terflies, we take up the question of the subdivision of the b.u.t.terflies into natural groups.
Various systems of arranging b.u.t.terflies have been suggested from time to time by learned writers, and for a knowledge of these systems the student may consult works which treat of them at length. It is sufficient for beginners, for whom this book is princ.i.p.ally written, to observe that in modern science, for purposes of convenience, as well as from regard for essential truth, all individuals are looked upon as belonging to a _species_. A species includes all those individuals, which have a common ancestry, and are so related in form and structure as to be manifestly separable from all other similarly const.i.tuted a.s.semblages of individuals. For instance, all the large cats having a tawny skin, and in the male a s.h.a.ggy mane, const.i.tute a species, which we call the lion; the eagles in the eastern United States, which in adult plumage have a snow-white head and neck and a white tail, const.i.tute a species, which we know as the "white-headed" or "bald-headed" eagle. Species may then be grouped together, and those which are manifestly closely related to one another are regarded as forming a natural a.s.semblage of species, to which we give the name of a _genus_. For example, all the large cats, such as the lion, the tiger, the puma, and the jaguar, are grouped together by naturalists, and form a genus to which is given the Latin name _Felis_, meaning _cat_. The name of the genus always comes before that of the species. Thus the tiger is spoken of scientifically as _Felis tigris_. The genera which are closely related to one another may again be a.s.sembled as _subfamilies_; and the subfamilies may be united to form _families_. For instance, all the various genera of cats form a family, which is known as the _Felidae_, or the Cat Family. A group of families const.i.tutes a _suborder_ or an _order_. The cats belong to the _Carnivora_, or order of flesh-eating animals.
In zoology family names are formed with the termination _-idae_, and subfamily names with the termination _-inae_.
Everything just said in regard to the cla.s.sification of the higher animals applies likewise to b.u.t.terflies. Let us take as an ill.u.s.tration the common milkweed b.u.t.terfly. Linnaeus for a fanciful reason gave this insect the name _Plexippus_. This is its specific name, by which it is distinguished from all other b.u.t.terflies. It belongs to the genus _Anosia_. The genus _Anosia_ is one of the genera which make up the subfamily of the _Euploeinae_. The _Euploeinae_ belong to the great family of the _Nymphalidae_. The _Nymphalidae_ are a part of the suborder of the _Rhopalocera_, or true b.u.t.terflies, one of the two great subdivisions of the order _Lepidoptera_, belonging to the great cla.s.s _Insecta_, the highest cla.s.s in the subkingdom of the _Arthropoda_. The matter may be represented in a tabular form, in the reverse order from that which has been given:
Subkingdom, _Arthropoda_.
Cla.s.s, _Insecta_.
Order, _Lepidoptera_.
Suborder, _Rhopalocera_.
Family, _Nymphalidae_.
Subfamily, _Euploeinae_.
Genus, _Anosia_.
Species, _Plexippus_ (Milkweed b.u.t.terfly).
_Varieties._--A still further subdivision is in some cases recognized as necessary. A species which has a wide range over an extensive territory may vary in different parts of the territory within which it is found. The b.u.t.terflies of certain common European species are found also in j.a.pan and Corea, but, as a rule, they are much larger in the latter countries than they are in Europe, and in some cases more brightly colored. Naturalists have therefore distinguished the Asiatic from the European form by giving the former what is known as a varietal name. Similar differences occur among b.u.t.terflies on the continent of North America. The great yellow and black-barred swallowtail b.u.t.terfly known as _Papilio turnus_ occurs from Florida to Alaska. But the specimens from Alaska are always much smaller than those from other regions, and have a very dwarfed appearance. This dwarfed form const.i.tutes what is known as a local race, or variety, of the species.
The members of a species which occur upon an island frequently differ in marked respects from specimens which occur upon the adjacent mainland.
By insulation and the process of through-breeding the creature has come to acquire characteristics which separate it in a marked degree from the closely allied continental form, and yet not sufficiently to justify us in treating it as a distinct species. It represents what is known as an insular race, or variety, and we give it therefore a varietal name.
Naturalists also distinguish between seasonal, dimorphic, melanic, and albino forms. Names descriptive or designatory of these forms are frequently applied to them. All of this will become plainer in the course of the study of the succeeding pages, and in the effort to cla.s.sify specimens which the student will make.
_s.e.x._--The designation of the s.e.x is important in the case of all well-ordered collections of zoological specimens. As a measure of convenience, the male is usually indicated by the sign of Mars, ?, while the female is indicated by the sign of Venus, ?. The inscription, "_Argynnis Diana_, ?," therefore means that the specimen is a male of _Argynnis Diana_, and the inscription, "_Argynnis Diana_, ?," means that the specimen is a female of the same species. These signs are invariably employed by naturalists to mark the s.e.xes.
_The Division of b.u.t.terflies into Families._--Without attempting to go deeply into questions of cla.s.sification at the present point, it will be well for us to note the subdivisions which have been made into the larger groups, known as families, and to show how b.u.t.terflies belonging to one or the other of these may be distinguished from one another.
There are five of these families represented within the territory of which this book takes notice. These five families are the following:
1. The NYMPHALIDae, or "Brush-footed b.u.t.terflies."
2. The LEMONIIDae, or "Metal-marks."
3. The LYCaeNIDae, or "Blues," "Coppers," and "Hair-streaks".
4. The PAPILIONIDae, or the "Swallowtails" and their allies.
5. The HESPERIIDae, or the "Skippers."
The NYMPHALIDae, the "Brush-footed b.u.t.terflies."