3i6 THE BIOLOGY OF INSECTS 



hindwing. There are no cercopods. The larvae are typical 

 caterpillars with strong mandibulate head, soft-coated body 

 often tubercled and hairy or spiny, with (usually) five pairs 

 of abdominal pro-legs besides the six thoracic legs (Figs. 5, 

 45). The pupa is rarely free and mandibulate ; usually it 

 becomes obtect, with wings and limbs adherent to the body. 



Sub-order i. HOMONEURA 



This group comprises only four or five families in 

 which the hindwing has as many nervures as the 

 forewing. In two of these families the pupa is free and 

 mandibulate. 



Sub-order ii. HETERONEURA 



This group comprises all the rest of the Lepidoptera 

 — perhaps fifty families — in which the radial nervure 

 is simple in the hindwing while in the forewing its 

 normal five branches are present. The pupa is never 

 mandibulate and always more or less obtect. 



Order 20. DIPTERA 



The Two-winged Flies have a specialised sucking labium 

 without palps ; mandibles and maxillae may serve as piercers 

 (Fig. 7). The forewings only are developed for flight, the 

 hindwings being knobbed halteres (" balancers "). The 

 larvae are cruciform grubs without true limbs, but often 

 bearing pro-legs (Fig. 72, c), or headless maggots (Fig. 51). 



Sub-order i. NEMATOCERA 



These are Diptera whose feelers are elongate, with 

 seven or more segments. All the larvae have a definite 

 head- capsule and the pupal cuticle splits longitudinally 

 for the emergence of the fly (Orthorrhapha). 



Sub-order ii. BRACHYCERA 



These are Diptera, the terminal region of whose 

 feelers is suppressed so that there appear to be only 



