155 



"bugs, cannot live away from the body of the host. The 

 louse, when feeding, holds on firmly by its powerful re- 

 curved and ridged claws to hairs or underclothing ; the 

 head is bent down, and the proboscis is thrust obliquely 

 forwards into the skin. Pediculus capitis is the species 

 usually found on the head, P. vestimenti is the clothes or 

 body-louse, and Phthirus pubis, the crab-louse, is a short 

 quat form infesting the pubic parts of the human body. 

 Lice are a result of personal uncleanliness ; but these 

 noxious parasites are often accidentally acquired by clean 

 persons through contact with verminous individuals, 

 and in other ways. Crowded conditions and body neglect 

 <e.g., troops on campaign) favour the spread of pediculosis. 

 The Clothes Louse is a carrier of the typhus virus ; and 

 the spirochaetes (Spiroschaudinniae) of European and 

 North African relapsing fever are also conveyed by it and 

 by the Head Louse. (See " Catechism" Zoology, Part I., 

 page 47). Phthirus pubis often causes dermatitis. Lice 

 Are also suspect in relation to tubercle, plague, leprosy, and 

 other diseases. 



Mention some Insects of Economic Importance. 



Injurious Insects. Locusts, saw-flies, many beetles, and 

 their larvae, e.g., Anobium, Scolytus, '* wireworm " larvae. 

 The larvae of certain butterflies and of many moths destroy 

 crops, produce, etc. The Hessian-fly is a serious pest of 

 cereal crops. Some species of Hemiptera (Bugs) are very 

 injurious, e.g., Oxycarenus (the Egyptian Cotton-stainer) 

 which damages cotton, Phylloxera which is destructive 

 to vines, and Cryptococcus, a dreaded pest of arboriculture. 

 Also blood-sucking, germ-carrying, and parasitic insects. 

 (See pages 142-147.) 



Beneficial Insects. Honey-bees, Ichneumon flies, certain 

 beetles, e.g., Scarabaeus, Burying beetles, Ladybirds, Blister- 

 beetle or Spanish-fly " ( Cantharis, syn. Lytta). The larvae 

 -of Silkworm Moths, the maggots of Hover-flies, the 

 Cochineal insect ( Coccus cacti), and Carteria which pro- 

 duces lac, these are also useful species. 



