THE ARTHROPODS 



399 



live in water and breathe by means of feathery gills on the 

 abdomen (Fig. 140). The larvae of mosquitoes have special 

 breathing tubes which can be extended above the surface 

 of the water. Larvae of lepidoptera which crawl on plants 

 have false legs for supporting the posterior end of the 

 body; but those of flies, beetles, ants, bees, etc., develop 

 in situations where such extra legs are not 

 required and they have only the three pairs 

 of thoracic legs. 



In various ways protective structures for 

 larvae are formed, and organs are specially 

 adapted for such work. Examples are : 

 spinning silky cocoons (by moth larvae), 

 making honeycomb (by adult bees), mak- 

 ing paper (by adult wasps), making cases 

 or tubes from bits of plants or gravel (by FIQ 14Q 

 caddis larvae), and rolling leaves to form 

 tubes (by many larvae) . 



Aquatic insects are especially noteworthy 

 for their adaptations. In some species oar- 

 like legs are fitted for locomotion by swim- 

 ming, and others for " skating " on water. 

 Mosquito larvae propel themselves by "wriggling" of the 

 abdomen. Some aquatic larvae (e.g., mosquito pupae) are 

 so filled with air that they float at the surface and can de- 

 scend only by swimming. A velvety covering of hairs on 

 the body and legs enables some insects to skate on the surface 

 film of water. The silvery white of the "backswimmers" 

 is due to a layer of air held by delicate hairs. Other aquatic 

 beetles and bugs have air-spaces beneath the front wings. 

 Special insect books describe many adaptations to aquatic life. 



Adaptations of insects with respect to color are so impor- 

 tant that a separate section of this chapter is devoted to them. 



333. Colors of Insects. Many insects are colored in 

 ways which are apparently useful to them. Such useful 



Larva of 

 May fly, with 

 feathery gills along 

 side of the abdo- 

 men adapting to 

 aquatic larval life. 

 (From Parker and 

 Haswell.) 



