ORDER PLATTPTERA. 



65 



meso- and metanotum are remarkable on account of the 

 imperfectly formed scuta and scutella, the latter being in- 

 definite in outline, though large. The chest-pieces (or 

 sterna) are large and broad; and there are often eleven seg- 

 ments in the abdomen. The order receives its name from 

 the fact that the wings are usually laid flat upon the back 

 when the insect is at rest. 



The bird-lice (Mallophaga), though usually associated 

 with the true lice (which are wingless parasitic Hemiptera), 

 in reality seem to be degraded, wingless Platyptera, and in 



FIG. 49. Tennes flavipes, white ant. o, larva; b. winged male; c, worker; d, 

 soldier; e, large female; /, nymph or pupa. From Riley. 



the shape of the body and mouth-parts are more nearly 

 allied to the family Psocidce, which includes the death- 

 tick, than any other group of insects; hence we regard 

 these parasites as forming a sub-order of the present group. 

 All the insects of this order have some remarkable peculiar- 

 ities. The stone-flies or Perlidae, which as larvae live in the 

 water and breathe by external tufts of gills growing on the 

 under side of the thorax, in some cases, as in the species of 

 Pteronarcys, retain them in the winged state. 

 5 



