INSECTA 487 



themselves with some foreign substance (Fig. 337), building a form 

 of tube from the wide end of which the head projects. Respiration 

 is effected by tracheal gills generally found on the abdomen, water 

 currents being passed through the tubular case by the undulatory 

 movements of the body. The larvae may be herbivorous or carnivor- 

 ous. Pupation usually takes place within the case after the openings 

 to the case have been closed by silk. The pupa is provided with large 

 mandibles by means of which it releases itself before the emergence 

 of the adult. The free pupa swims to the water's edge by means of its 

 mesothoracic legs and shortly afterwards the adult emerges. Common 

 caddis flies are Phryganea, Limnophilus and Rhyacophila. 



Fig. 337. A, B, C, D, Cases of Trichoptera. A, Hydroptila maclachlani. 

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

 guttatipennis. After Imms. 



Order LEPIDOPTERA (Butterflies and moths) 



Mouth parts of the imago usually represented only by a sucking pro- 

 boscis formed by the maxillae; two pairs of membranous wings, 

 clothed with flattened scales, as also is the body; metamorphosis 

 complete; larvae cruciform with masticating mouth parts, with three 

 pairs of legs on the thorax and often five pairs of prolegs on the 

 abdomen; pupae obtect, either enclosed in a cocoon or an earthen 

 case, or free. 



The imagines live on the nectar of flowers, and to absorb this a 

 highly specialized proboscis has been formed from the greatly elon- 

 gated galeae of the maxillae, each being grooved along its inner face 

 and locked to its neighbour (Fig. 338). The laciniae are atrophied 

 and the maxillary palp is usually much reduced. The mandibles are 



