HEXAPODA (Insecta)
The Thysanura (springtails and bristletails), the Neuropteroids (may-flies, stone-flies, dragon-flies, caddis-flies, etc.), Mallophaga (bird lice), Physopoda (thrips), Orthoptera (gra.s.shoppers, crickets, roaches), are of no special interest from our viewpoint. The remaining orders are briefly characterized below.
SIPHUNCULATA (page 275)
Mouth parts suctorial; beak fleshy, not jointed; insect wingless; parasitic upon mammals. Metamorphosis incomplete. Lice.
HEMIPTERA (page 275)
Mouth parts suctorial; beak or the sheath of the beak jointed; in the mature state usually with four wings. In external appearance the immature insect resembles the adult except that the immature form (i.e.
nymph) never has wings, the successive instars during the process of growth, therefore, are quite similar; and the metamorphosis is thus incomplete. To this order belong the true bugs, the plant lice, leaf hoppers, frog hoppers, cicadas, etc.
LEPIDOPTERA
The adult insect has the body covered with scales and (with the rare exception of the females of a few species) with four wings also covered with scales. Proboscis, when present, coiled, not segmented, adapted for sucking. Metamorphosis complete, i.e. the young which hatches from the egg is quite unlike the adult, and after undergoing several molts transforms into a quiescent pupa which is frequently enclosed in a coc.o.o.n from which the adult later emerges. The larvae are known as caterpillars. b.u.t.terflies and moths.
DIPTERA (page 285)
The adult insect is provided with two, usually transparent, wings, the second pair of wings of other insects being replaced by a pair of halteres or balancers. In a few rare species the wings, or halteres, or both, are wanting. The mouth parts, which are not segmented, are adapted for sucking. The tarsi are five-segmented. Metamorphosis complete. The larvae, which are never provided with jointed legs, are variously known as maggots, or grubs, or wrigglers. Flies, midges, mosquitoes.
SIPHONAPTERA (page 316)
Mouth parts adapted for sucking; body naked or with bristles and spines; prothorax well developed; body compressed; tarsi with five segments; wings absent. Metamorphosis complete. The larva is a wormlike creature.
Fleas.
COLEOPTERA
Adult with four wings (rarely wanting), the first pair h.o.r.n.y or leathery, veinless, forming wing covers which meet in a line along the middle of the back. Mouth parts of both immature stages and adults adapted for biting and chewing. Metamorphosis complete. The larvae of many species are known as grubs. Beetles.
HYMENOPTERA
Adult insect with four, usually transparent, wings, wanting in some species. Mouth parts adapted for biting and sucking; palpi small; tarsi four or five-segmented. Metamorphosis complete. Parasitic four-winged flies, ants, bees, and wasps.
SIPHUNCULATA AND HEMIPTERA
a. Legs with claws fitted for clinging to hairs; wings wanting; spiracles of the abdomen on the dorsal surface. (= ANOPLURA = PARASITICA) SIPHUNCULATA.
b. Legs not modified into clinging hooks; tibia and tarsus very long and slender; tibia without thumb-like process; antennae five-segmented HaeMATOMYZIDae Endr.
_Haematomyzus elephantis_ on the elephant.
bb. Legs modified into clinging hooks; tibia and tarsus usually short and stout; tibia with a thumb-like process; head not anteriorly prolonged, tube-like.
c. Body depressed; a pair of stigmata on the mesothorax, and abdominal segments three to eight; antennae three to five-segmented.
d. Eyes large, projecting, distinctly pigmented; pharynx short and broad; fulturae (inner skeleton of head) very strong and broad, with broad arms; proboscis short, scarcely attaining the thorax. PEDICULIDae
e. Antennae three-segmented. A few species occurring upon old world monkeys. _Pedicinis_ Gerv.
ee. Antennae five-segmented.
f. All legs stout; thumb-like process of the tibia very long and slender, beset with strong spines, fore legs stouter than the others; abdomen elongate, segments without lateral processes; the divided telson with a conical process posteriorly upon the ventral side. PEDICULUS L.
g. Upon man.
h. Each abdominal segment dorsally with from one to three more or less regular transverse rows of small setae; antenna about as long as the width of the head. Head louse (fig. 65). P. HUMa.n.u.s.
hh. "No transverse rows of abdominal setae; antenna longer than the width of the head; species larger." Piaget.
Body louse of man. P. CORPORIS.
gg. Upon apes and other mammals. _P. pusitatus_ (?).
ff. Fore legs delicate, with very long and slender claws; other legs very stout with short and stout claws; thumb-like process of the tibia short and stout; abdomen very short and broad; segment one to five closely crowded, thus the stigmata of segments three to five apparently lying in one segment; segments five to eight with lateral processes; telson without lateral conical appendages (fig.
69). Crab louse of man. PHTHIRUS PUBIS.
dd. Eyes indistinct or wanting; pharynx long and slender, fulturae very slender and closely applied to the pharynx; proboscis very long. Several genera found upon various mammals.
HaeMATOPINIDae.
cc. Body swollen; meso- and metathorax, and abdominal segments two to eight each with a pair of stigmata; eyes wanting; antennae four or five-segmented; body covered with stout spines. Three genera found upon marine mammals. ECHINOPHTHIRIIDae
aa. Legs fitted for walking or jumping; spiracles of abdomen usually ventral; beak segmented.
b. Apex of head usually directed anteriorly; beak arising from its apex; sides of the face remote from the front c.o.xae; first pair of wings when present thickened at base, with thinner margins.
HETEROPTERA
[Ill.u.s.tration: 159. Taxonomic details of Hemiptera-Heteroptera. (_a_) Dorsal aspect; (_b_) seta from bedbug; (_c_) wing of Heteropteron; (_d_) leg; (_e_) wing of Sinea.]
c. Front tarsi of one segment, spade-form (palaeformes); beak short, at most two-segmented; intermediate legs long, slender; posterior pair adapted for swimming. CORIXIDae
cc. Front tarsi rarely one-segmented, never spade-form; beak free, at least three-segmented.
d. Pulvilli wanting.
e. Hemelytra usually with a distinct clavus (fig. 159), clavus always ends behind the apex of the scutellum, forming the commissure. (Species having the wings much reduced or wanting should be sought for in both sections.)
f. Antennae very short; meso- and metasternum composite; eyes always present.
g. Ocelli present; beak four-segmented. OCHTERIDae and NERTHRIDae.