The Classification of Insects 
55 
HH. Hind wings, when present, not broader than fore 
wings, not jolded in repose; prothorax small } 
collar-like. 
I. Tarsi jour-jointed; wings, when present, 
equal in size .(Termites.) Isoptera. 
II. Tarsi one- to three-jointed. 
J. Tarsi one- or two-jointed; always 
wingless. 
(Biting bird-lice.) Mallophaga. 
JJ. Tarsi usually three-jointed; occasionally 
two-jointed, in which case wings always 
present, fore wings larger than hind 
wings. (Book-lice, etc.) Corrodentia. 
GG. Tarsi jive-jointed, but with one joint sometimes 
dijjicult to distinguish; labium usually entire in 
middle, sometimes slightly emarginate. 
H. Wings, when present, naked or slightly hairy; 
hind wings with or without jolded anal space; 
in jormer case prothorax large and nearly 
plat on dorsal surjace; in wingless jorms 
mouth prolonged into a distinct beak. 
I. Mouth-parts not prolonged into a distinct 
beak, at most slightly conical. 
(Dobsons, ant-lions, etc.) Neuroptera. 
II. Mouth-parts prolonged into a distinct beak. 
(Scorpion-flies, etc.) Mecoptera. 
HH. Wings, when present, thickly covered with hairs; 
hind wings usually with jolded anal space; pro¬ 
thorax small, collar-like; mouth not prolonged 
into a beak. (Caddis-flies.) Trichoptera. 
DD. Fore wings, when present, veinless; horny or leathery; when absent, 
labium entire, and mouth-parts not prolonged into a distinct beak. 
(Beetles.) Coleoptera. 
BB. Mouth-parts, when developed, more or less pitted jor sucking; sometimes also 
pitted in part (the mandibles) jor biting: in this case either (i) base oj abdomen 
usually strongly constricted, joined to thorax by a narrow peduncle, or (2) the 
tarsi bladder-shaped, without claws; when mouth is rudimentary either the 
wings are two and halteres are present, or the wings are four or none and 
the body (and wings if present) are densely clothed with scales. 
C. Prothorax jree; body (and wings ij present) never densely clothed with 
scales; maxillary palpi usually absent; when present, tarsi bladder¬ 
shaped, without claws. 
D. Tarsi bladder-shaped, without claws; wings jour (sometimes absent ), 
narrow, jringed with long hairs; maxillae triangular, with palpi. 
(Thrips.) Thysanoptera. 
DD, Tarsi not bladder-shaped, usually clawed; wings not jringed with 
long hairs; maxilla (when mouth is developed ) bristle-like, without 
palpi. (Bugs.) Hemiptera. 
CC. Prothorax not jree; maxillary palpi present, sometimes rudimentary 
and difficult to see, in which case body (and wings if present) densely 
clothed with scales; tarsi never bladder-shaped, usually clawed. 
