80 BRITISH INSECTS 



at the extremity of the abdomen, which serve to anchor 

 the creature to its case. Breathing is effected by 

 thread-like gills that trail from certain of the ab- 

 dominal segments, and are constantly bathed with 

 water, which circulates freely in the space between 

 the larva's body and the inner wall of its abode. 

 After feeding for several months, the larva closes both 

 ends of its case with a webbing of silk, and changes 

 to a free pupa (p. 62), which closely resembles the 

 mago, save that it is equipped with powerful man- 

 dibles. The latter serve to bite a way out of the case, 

 and are discarded with the pupal skin at the final 

 moult. After effecting its escape, the pupa swims to 

 the surface of the water, using its middle legs, which 

 are developed like oars for the purpose. It then 

 climbs up some convenient stem or post ; its skin 

 splits down the back, and the perfect insect emerges. 

 There are about 150 British caddis-flies, the large 

 species of the genus Phryganea (whose larvae inhabit 

 still waters) being most likely to attract attention. 



Moths and butterflies make up the fifteenth order, 

 or Lepidoptera, which gets its name from the minute 

 overlapping scales which clothe the bodies and 

 wings of the insects concerned. In the adults of 

 certain families all the mouth-parts are rudimentary, 

 and no food is taken ; but usually the first maxillae 

 are elongated and grooved on their inner surfaces, so 

 that when in apposition they form a tube, or proboscis, 

 through which liquids can be sucked into the mouth. 

 The other mouth-parts are generally very small or 

 absent, except the palpi of the second maxillae, which 

 are w r ell developed. We have already seen that in 

 the lowest families of moths a jugum is present at the 

 base of each fore-wing. Most other moths have a 



