RHYNCOTA. 27 



entirely in the water, but the majority are aerial. The 

 Order is divided into three sub-orders, viz. : — the 

 Anopluray the Heteroptera, and the Homoptera. The 

 Anopliira contain all those insects commonly known as 

 lice, which are parasitic on man and other animals. 

 The suctorial louse {pedlculus), of which four species 

 are parasitic on man, belong to this sub-order ; it also 

 includes all the biting bird-lice, which by some writers 

 have been made into a separate order under the name 

 of Mallophaga. But it is better to arrange the bird- 

 li^ notwithstanding the difference of structure in the 

 mouth, with the Anoplura. Nearly 500 different forms 

 of these parasitic insects, formed oh the plan of the 

 common louse, have been described. Almost every bird 

 has its parasite accompaniments, and several of the 

 Mammalia have theirs. Some animals have only one 

 species of parasite peculiar to itself, others have 

 several species ; on domestic cattle three species are 

 found, on the horse _two^ on the ass three; on the 

 golden eagle four, on the white-tailed eagle no less than 

 six species of parasitic louse occurs, and water birds are 

 as subject to them as land birds. These biting-lice do 

 not suck the blood like the common pediculus, but eat 

 the delicate parts of the feathers or hair. The Anoplura 

 undergo no metamorphosis ; the eggs are hatched in a 

 few days, and the young are soon capable of repro- 

 duction, hence the enormously rapid increase where 

 strict measures are not adopted for their extermination. 

 I believe it was Leeuwenhoek who computed that in two 

 months two female lice could produce ten thousand ! 

 The Heteroptera include those insects of the Order 

 Rhyncota, whose anterior wings are heterogeneous, i.e.y 



