A carina 
273 
j. Body with fewer, longer hairs; often spinning threads; 
no dorsal groove; tarsi never swollen; mandibles 
styhform (for piercing). TETRANYCHID® 
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. . . . Rhycholophid.-e. 
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), Phvsopoda (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 
