BULLETIN 39, UNITED STATKS NATIONAL Ml'SEl'M. 



figure. XollinixorirorHx has been observed by Dr. Packard to eat the 

 eggs of the Canker Worm. 



Tlit- members of the family Gamasidai are ]arasitie upon animals, 

 but chiefly upon insects. The Hydrachnida> are parasitic also upon the 



aquatic insects, and also affecl lisli or mussels or 

 occur on fresh-water plants. . 



One of the most important families of mites is 

 the Trombidiidijie which includes a large number 

 of species, some of which occur in immense num- 

 bers. Most of them are vegetable feeders, but 

 some species feed on the eggs of insects. 



The genus Trombidium includes a number of 

 the Red Mites which feed on insects in all then- 

 stages. The Locust Mite, TrombMhun lonixinni.ii 

 Riley, is one of the most interesting as well as one 

 of the most important of our locust enemies, and will serve to illustrate 

 the habits of the group. It differs so much in infancy and maturity that 

 it has been referred to different genera and is known under different 

 names. The mature form lives on the ground and feeds on all sorts of 

 animal or decomposing vegetable matter, and wherever the ground is 

 tilled with locust eggs these afford an abundance of food and the mites 

 flourish and multiply rapidly. In the spring the female lays ;ino or 400 



FIG. 135. Nothrus ovivorus 

 Packard. 



1 K.. i:;ti.~ -Tf,,inl,iili<nit I'.cuxttn-inii : a, 1'rnialr with her hatch of eggs; (>, newly hatched lar\a - 

 natural si/.- indicated by the dot within the circle: c, cu'.ii; d c, varatcd i-.^u 



minute spherical orange-red rggs in the grnnnd (Fig. l.'Ui^.. l-'rom 

 the>e eggs, as shou ii rnhirged a) C, il, and t- (the two latter l.eing the 

 \ aeaied egg sliells) enier-c the six-legged larva, shown at l>. These are 

 mere specks and crawl actively about, fastening themselves to the 

 locusts mostly at the base of the wings or along the upper veins. 

 They subsist on the juices of their host. They (irmly attach themselves 

 by the mouth and increase rapidly in si/.e, the legs not growing and 

 becoming mere rudiments. In this form they are shown at Fig. i::7<f. 

 When fully developed they let go their hold, drop to the ground, and 



