146 HYMENOPTEEA. 



to form a net-work * Their economy in the early stages 

 of their growth is very curious. The larva, which is not 



Fig. 105. — PUPA CASE, laeva, and fly of caddis-wokm. 



unlike a caterpillar, forms for its residence a tubular case, 

 made of minute shells, stones, seeds, bits of stick or bark, 

 fragments of the stems of water-plants, and similar matters, 

 which it arranges around its body, fixing them by means 

 of a glutinous silk, vfhich also lines the tube. Numbers 

 of these cases may often be seen at the bottom of pebbly 

 streams, with the head and feet of the larva protruding 

 from one end as it crawls about, with a straggling irregular 

 motion. When full grown, the little creature creeps up 

 the stem of some aquatic plant till the mouth of its case 

 just reaches the surface of the water ; it then spins a net 

 of silk across the entrance to its abode, and goes into the 

 pupa state. At the appointed time the pupa tears its way 

 easily through the silken grate, crawls a few inches out of 

 the water, thi'ows off its pupa skin, and becomes a winged 

 caddis-fly. 



Order HYMENOPTERA.t 



The Hymenopterous insects, like the Neuroptera, 

 are furnished with four transparent wings, but instead 

 of the nervures forming a close net-work, they are 

 much more sparingly distributed. Another difference 

 is that in the Hymenoptera the hind pair of wings 

 seem as if cut out of the front pair, -with which they 

 interlock by means of small hooks during flight, so 

 that the two wings almost resemble one. The 

 abdomen is, moreover, terminated by an apparatus, 



* Some authors constitute a distinct order for them, under the 

 name of Trichoptera, or Hairy- winged insects. 



t vfx^y, umeu, a membrane ; trrepoy, pteron, a loing. 



