TROMBIDIIDAE OF MINNESOTA ILI 
condition the larval skin hardens and the nymph is formed inside. 
About one week is spent in the soil after which the nymph appears at 
the surface. Nymphs are found from late June to late July. They re- 
semble the adult closely except for size, and feed as do the adults on 
aphids and other insects. By late July they enter the soil once more or 
hide in curled up dried leaves at the surface. The skin hardens and in- 
side is formed the adult mite. In about two weeks the adult bursts the 
old dried nymph skin and crawls to the surface of the soil. From this 
time, early to late August, onward, the adults feed until cold weather 
when they enter the soil once more and remain until early spring. 
Altho somewhat localized in distribution this species must 
be very beneficial, especially in the control of aphids, as every stage 
feeds upon them, even destroying the winter eggs. It seems to have 
few enemies. Rove beetles in one of the breeding jars were seen to 
eat the adults and ants were seen attempting to carry them away. No 
other insect has been seen, however, to prey upon them in the field or 
in breeding jars, nor have any parasites been reared from them. 
The larvae of this species seem to have no relation to the “chigger”’ 
pest. On several occasions large numbers were placed inside the writ- 
ers stocking or underwear, but in no case did one attempt to penetrate 
the skin. Where they are most abundant there seems to be little 
trouble from “Chiggers.” 
Eutromlidium locustarum (Walsh). 
Astoma locustarum Walsh, Practical Entomology, Vol. I p. 126; 
1886 LeBaron, Ill. Report. 2, p. 61; 1875. 
Astoma gryllaria Riley. 7th Missouri Report, p. 176; 1875. 
Trombidium locustarum Riley, Rpt. U. S. Ent. Comm. p. 306; 
1878. 
Ottonia locustarum Banks, Trans. Am. Ent. Soc.: Vol. 21, p. 213; 
1894. 
Microtrombidium locustarum Ewing. System. and Biol. Study of 
Acarina of Ill. Univ. Studies, Univ. Ill. Vol. 3, p. 94; 1909. 
Adult female. Color, scarlet, darkening with age, in certain lights 
the folds on the abdomen have a whitish reflection, under side brighter 
than dorsal. Size, 2.75 to 3 mm. long by 2 mm. wide. When en- 
gorged may reach a length of 4 mm. long by 2.50 mm. wide. Body 
covered with slender plumose hairs; constricted near the middle, wider 
in anterior half, a deep transverse groove at the line of constriction, a 
second near the middle of the wide anterior half; a large trapezoidal 
chitinous plate at the posterior end of the dorsum, nearly a third as 
iong as the abdomen, and a little longer than wide; a shallow arched 
