THE LOWER ORDERS 



37 



gnawed off. The function of these individuals is repro- 

 duction only. 



The workers are of both sexes but are not fully devel- 

 oped sexually. They do all the work pertaining to the 

 colony and are blind and avoid the light. They are 

 wingless. Soldiers are like the workers but have ex- 

 traordinarily large heads. Their function is said to be the 

 defense of the colony, but there is considerable doubt as 

 to their efficiency. 



30. Mallophaga.* The members of this order are called 

 Bird-lice or Biting-lice, but are found as often on various 

 species of mammals as on birds. 



They are wingless, have biting 

 mouth-parts and rather slender, 

 flattened bodies. They feed on 

 feathers, hair and scales of the 

 epidermis. They injure their 

 hosts rather by irritating them 

 than in any other way. Different 

 kinds may be found on poultry 

 and on most of the domestic 

 animals, as well as on many 

 kinds of wild birds and mam- 

 mals. 



31. Siphunculata.f This group is composed of the 

 True lice or the Sucking-lice. They resemble the bird lice 

 superficially but are usually broader and more flattened 

 and have short fleshy beaks by means of which they suck 

 blood from their hosts, which are mammals. Three spe- 

 cies attack man and some others are known to attack 

 marine mammals, thus invading a field in which insects 



* See Fig. 142, page 200, Part II. 



f See Figs. 140 and 141, pages 198, 199, Part II. 



FIG. 23. A Bird-louse (Mal- 

 lophaga) . Highly magnified. 



