1. _Heteroptera_: Rostrum not in contact with haunches of fore-legs.
Fore-wings partly coriaceous. Young resembling adults.
Includes the bugs, terrestrial and aquatic.
2. _Homoptera_: Rostrum in contact with haunches of fore-legs.
Fore-wings uniform in texture. Young often larvae. Penultimate instar
passive in some cases.
Includes the cicads, aphides and scale-insects (see HEMIPTERA).
Order: _Anoplura_.
Piercing jaws modified and reduced, a tubular, protrusible
sucking-trunk being developed; mouth with hooks. Wingless, parasitic
forms. Cerci absent. Four Malpighian tubes. Young resembling adults.
Includes the family of the Lice (_Pediculidae_), often reckoned as
Hemiptera (q.v.). See also LOUSE.
Sub-class: ENDOPTERYGOTA.
Hexapoda mostly with wings; the wingless forms clearly degraded or
modified. Maxillulae vestigial or absent. No locomotor abdominal
appendages (except in certain larvae). Young animals always unlike
parents, the wing-rudiments developing beneath the larval cuticle and
only appearing in a penultimate pupal instar, which takes no food and
is usually passive.
Order: _Neuroptera_.
Biting mandibles; second maxillae completely fused. Prothorax large
and free. Membranous, net-veined wings, those of the two pairs closely
alike. Six or eight Malpighian tubes. Cerci absent. Larva
campodeiform, usually feeding by suction (exceptionally
hypermetamorphic with subsequent eruciform instars). Pupa free.
Includes the alder-flies, ant-lions and lacewing-flies. See
NEUROPTERA.
Order: _Coleoptera_.
Biting mandibles; second maxillae very intimately fused. Prothorax
large and free. Fore-wings modified into firm elytra, beneath which
the membranous hind-wings (when present) can be folded. Cerci absent.
Four or six Malpighian tubes. Larva campodeiform or eruciform. Pupa
free.
Includes the beetles and the parasitic _Stylopidae_, often regarded as
a distinct order (_Strepsiptera_). (See COLEOPTERA.)
Order: _Mecaptera_.
Biting mandibles; first maxillae elongate; second maxillae completely
fused. Prothorax small. Two pairs of similar, membranous wings, with
predominantly longitudinal neuration. Six Malpighian tubes. Larva
eruciform. Pupa free. Cerci present.
Includes the single family of _Panorpidae_ (scorpion-flies), often
comprised among the Neuroptera.
Order: _Trichoptera_.
Mandibles present in pupa, vestigial in imago; maxillae suctorial
without specialization; first maxillae with lacinia, galea and palp.
Prothorax small. Two pairs of membranous, hair-covered wings, with
predominantly longitudinal neuration. Larvae aquatic and eruciform.
Pupa free. Six Malpighian tubes. Cerci absent.
Includes the caddis-flies. See NEUROPTERA, among which these insects
were formerly comprised.
Order: _Lepidoptera_.
Mandibles absent in imago, very exceptionally present in pupa; first
maxillae nearly always without laciniae and often without palps, or
only with vestigial palps, their galeae elongated and grooved inwardly
so as to form a sucking trunk. Prothorax small. Wings with
predominantly longitudinal neuration, covered with flattened scales.
Fore-wings larger than hind-wings. Cerci absent. Four (rarely 6 or 8)
Malpighian tubes. Larvae eruciform, with rarely more than five pairs
of abdominal prolegs. Pupa free in the lowest families, in most cases
incompletely or completely obtect.
Includes the moths and butterflies. See LEPIDOPTERA.
Order: _Diptera_.
Mandibles rarely present, adapted for piercing; first maxillae with
palps; second maxillae forming with hypopharynx a suctorial proboscis.
Prothorax small, intimately united to mesothorax. Fore-wings well
developed; hind-wings reduced to stalked knobs ("halteres"). Cerci
present but usually reduced. Four Malpighian tubes. Larvae eruciform
without thoracic legs, or vermiform without head-capsule. Pupa
incompletely obtect or free, and enclosed in the hardened cuticle of
the last larval instar (puparium).
Includes the two-winged flies (see DIPTERA), which may be divided into
two sub-orders:--
1. _Orthorrhapha_: Larva eruciform. Cuticle of pupa or puparium
splitting longitudinally down the back, to allow escape of imago.
Comprises the midges, gnats, crane-flies, gad-flies, &c.
2. _Cyclorrhapha_: Larva vermiform (no head-capsule). Puparium opening
by an anterior "lid."
Comprises the hover-flies, flesh-flies, bot-flies, &c.
Order: _Siphonaptera_.
Mandibles fused into a piercer; first maxillae developed as piercers;
palps of both pairs of maxillae present; hypopharynx wanting.
Prothorax large. Wings absent or vestigial. Larva eruciform, limbless.
Includes the fleas.
Order: _Hymenoptera_.
Biting mandibles; second maxillae incompletely or completely fused;
often forming a suctorial proboscis. Prothorax small, and united to
mesothorax. First abdominal segment united to metathorax. Wings
membranous, fore-wings larger than hind-wings. Ovipositor always well
developed, and often modified into a sting. Numerous (20-150)
Malpighian tubes (in rare cases, 6-12 only). Larva eruciform, with
seven or eight pairs of abdominal prolegs, or entirely legless. Pupa
free.