ARACHNIDA 131 



and abdomen, as in true spiders. Phalangids are nocturnal. 

 They lurk in quiet nooks during the day and come out at 

 night to feed on small insects and other animals. Their 

 food habits make them beneficial to man. 



Fia. 60. Scorpion carrying young and killing a spider; phalangid eating a fly. 



ORDER 4. ACARINA 



This order includes the mites and ticks (Fig. 61). These 

 arachnids are wholly without external evidences of seg- 

 mentation. The body is not even divided into regions, 

 the head, thorax, and abdomen being fused into one mass. 

 Many of the ticks and mites are parasitic in their .habits 

 and some carry diseases. All are able to go for long periods 

 of time without food, sometimes for as much as three or 

 four years. 



The mites are all of small size and their bodies are never 

 greatly swollen. There are several important species in 

 the United States. The poultry mite, Dermanyssus gallince 

 sucks the blood of fowls and annually causes great losses. 

 The chiggers, or harvest mites, Trombididce, are common 

 on low vegetation and hence often get on men working in 

 fields. As six-legged larvae, they commonly attack the 

 skin and cause severe irritation. Preventative measures 

 consist in sprinkling powdered sulphur or naphelene in the 

 underclothing. Bites are treated with ammonia or weak 

 carbolic solution. The disease known as scabies or seven- 



