Acarina 273 



j. Body with fewer, longer hairs; often spinning threads; 

 no dorsal groove; tarsi never swollen; mandibles 



stylif orm (for piercing) TETRANYCHID^E 



The genus Tetranychus may be distinguished from the 



other genera occurring in the United States by the 



following characters: No scale-like projections on 



the front of the cephalothorax ; legs I as long or 



longer than the body ; palp ends in a distinct thumb ; 



the body is about 1.5 times as long as broad. T. 



molestissimus Weyenb. from South America, and 



T. telarius from Europe and America ordinarily 



infesting plants, are said also to molest man. 



jj. Body with many fine hairs or short spines; not spinning 



threads; often with dorsal groove; tarsi often 



swollen. 



k. Mandibles styliform for piercing. . . . RHYCHOLOPHHLE. 



kk. Mandibles chelate, for biting TROMBIDID^ 



The genus Trombidium has recently been sub- 

 divided by Berlese into a number of smaller 

 ones, of which some five or six occur in the 

 United States. The mature mite is not para- 

 sitic but the larvae which are very numerous in 

 certain localities will cause intense itching, 

 soreness, and even more serious complications. 

 They burrow beneath the skin and produce 

 inflammed spots. They have received the 

 popular name of "red bug," The names Leptus 

 americanus and L. irritans have been applied to 

 them, although they are now known to be im- 

 mature stages. (Fig. 44.) 



HEXAPODA (Insecta) 



The Thysanura (springtails and bristletails), the Neuropteroids 

 (may-flies, stone-flies, dragon-flies, caddis-flies, etc.), Mallophaga 

 (bird lice), Physopoda (thrips), Orthoptera (grasshoppers, crickets, 

 roaches), are of no special interest from our viewpoint. The remain- 

 ing orders are briefly characterized below. 



SIPHUNCULATA (page 275) 



Mouth parts suctorial; beak fleshy, not jointed; insect wingless; 

 parasitic upon mammals. Metamorphosis incomplete. Lice. 



HEMIPTERA (page 275) 



Mouth parts suctorial; beak or the sheath of the beak jointed; 

 in the mature state usually with four wings. In external appearance 



