TROMBIDIIDAE OF MINNESOTA 121 
even as late as early October. This unevenness in the life history 
is due to the delay which often occurs in the adult finding food in 
spring. The larvae attach themselves to any stage of the grasshopper 
from the first instar to the adult. They prefer to attach at a com- 
missure between the segments of the abdomen or thorax, especially 
under or on the wing pads, or at the joints of the tarsi or about the 
mouth. On adults they often attach on the veins of the wings. The 
reasons for attaching at such points are obvious, when their delicate 
mouth parts are considered. Almost any species of acridid may be 
chosen as host. We have fed them on Tettix sp., Melanoplus bivittatus, 
M. femur-rubrum, M. gladstoni, Stenobothris curtipennis, Orphulella 
speciosa and O. palidna. Anywhere from one to one hundred twenty- 
four larvae have been counted on a single grasshopper nymph. The 
orange colored larvae soon engorge to several times their original size, 
losing all resemblance to their previous form and resembling engorged 
female ticks in appearance. In fact they are popularly known as grass- 
hopper ticks. Engorgement may require as long as fourteen days. 
If it so happens that a larva has just attached to a nymph which is 
about to molt or is unable to penetrate the body wall and reach the 
body fluids and so not engorge readily, it will migrate to the moulted 
host after the skin is sloughed off, or to a more favorable part of the 
body. If, however, it has begun to engorge it is unable to migrate. 
Usually engorgement is completed between moults, or after the host 
has moulted to the adult stage. 
As soon as the larva is fully engorged, which occurs for the ma- 
jority by mid July, it drops off and enters the soil, burrowing from one 
quarter of an inch to one inch deep. The hardened larval skin acts as a 
cover for the developing nymph, which emerges in about five days. The 
nymph appears in late July to mid August when many grasshoppers are 
beginning to oviposit, and it at once searches for these eggs as food, 
altho at this time they may take other food than grasshopper eggs. We 
have had some partly engorge on angle worms and attempt to feed on 
larvae of M. domestica. The latter, however, proved too active. They 
will readily attack eggs removed from the oviducts of female grass- 
hoppers. After engorgement, which requires fourteen to twenty days, 
they again enter the soil and pass through a transformation stage from 
which the adult emerges. The adult may eat at this time or it may go at 
once into hibernation. Most of those in our breeding cages refused to 
eat. The mature adults appear during late August when many grass- 
hoppers are ovipositing. 
The economic importance of Eutrombidium locustarum is un- 
