426 THE INVERTEBRATA 



of cross veins divide the whole area into a number of nearly equal 

 rhomboidal cells. 



The male genitalia are prominent and the terminal segments of the 

 abdomen carry them in a dorsally curved position in the manner of 

 the scorpion's tail. The cruciform larvae are caterpillar-like and may 

 possess prolegs on all segments of the abdomen. This feature, to- 

 gether with the presence of a large number of ocelli on the head (there 

 may be twenty or more on each side), readily distinguishes these larvae 

 from those of the Lepidoptera. 



Panorpa communis, the common English scorpion fly, lays eggs in 

 crevices in the soil and the larvae hatching from these feed on decay- 

 ing organic matter. Pupation occurs in an earthen cell and the life 

 cycle is an annual one. Much information is still wanting on the life 

 histories of the members of this order. 



Order TRICHOPTERA (Caddis flies) 



Medium-sized insects with bodies and wings well clothed with hairs ; 

 mandibles vestigial or absent; maxillary and labial palps well de- 

 veloped; two pairs of membranous wdngs, with few cross veins and 

 held in a roof-like manner when at rest. 



Fig. 316. A, B, C, D, Cases of Trichoptera. A, Hydroptila maclachlani. 

 B, Odontocerum. C, Phryganea. D, Hydropsyche, pupal case. E, Halesus 

 guttatipennis . After Imms. 



The cruciform larvae are aquatic and usually live in cases formed of 

 such material as particles of wood, sand, small shells, etc. A pair of 

 hooked prolegs on the last abdominal segment which assists in 

 adhering to the case is a characteristic feature. 



