36 ENTOMOLOGY 
rentiation, the mouth parts are of fundamental importance to 
the systematist, particularly for the separation of insects into 
orders. Most of the orders fall into two groups according 
as the mouth parts are either biting (mandibulate) or sucking 
Wy 
WW D 
WN : NX Zip 
Antenne of mosquito, Culex pipiens. A, male; B, female. 
(suctorial). Collembola and Hymenoptera, however, com- 
bine both functions; Diptera, though suctorial, exhibit various 
modifications for piercing, lapping or rasping; Thysanoptera 
are partly mandibulate but chiefly suctorial; and adult Ephe- 
merida and Trichoptera have but rudimentary mouth parts. 
The mandibulate orders are Thysanura, Collembola (pri- 
marily), Orthoptera, Platyptera, Plecoptera, Ephemerida 
(rudimentarily in adult), Odonata, Neuroptera, Mecoptera 
and Coleoptera. 
The mouth parts of an insect consist typically of labrum, 
mandibles, maxille, labium and hypopharyny (Fig. 44), 
though these organs differ greatly in different orders of in- 
sects. The mandibulate, or primary type, from which the 
suctorial, or secondary type, has been derived, will be consid- 
ered first. 
Mandibulate Type.—The labrum, or upper lip, in biting 
