270 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Important internal parasites are species of Gordius or Mermis, 
hair-worms or 'hair-snakes,' thread-Hke creatures from several 
inches to a foot or two in length which develop in the body, pre- 
vent the normal growth of the organs, and finally weaken and kill 
their hosts. 
In early spring one often sees crawling over the ground or hid- 
ing under stones in fields where Locusts were numerous the pre- 
vious autumn, numbers of small scarlet mites, with eight legs and 
a plump, velvety body. These are adults of the locust-mite, 
Tromhidium locustarum. The females soon lay 300 to 400 eggs 
in a chamber in the soil, from which in due season hatch tin}', 
six-legged, very active young. These attach themselves at the 
first opportunity to young Locusts by means of their sucking 
mouth-parts, usuallj' in some protected situation where the body- 
wall is thin, such as under the free edge of the pronotum or between 
the wing-pads, where they remain, even after the Locust becomes 
mature, sucking out its life fluids, growing corpulent at the 
expense of their host, which is usually much weakened by their 
presence and hops and flies clumsily. When full-grown, the 
larval mites drop to the ground, enter the pupal state, and later 
on, sometimes in autumn, sometimes not until spring, become 
adults. Locusts bearing numbers of these mites upon their 
wings are common objects in the fall, and I have seen them so 
heavily infested as to appear red-winged at a little distance, 
from this cause. Even the locust eggs are attacked by these 
mites while burrowing in the soil, and many are destroyed at that 
time. The eggs are also devoured by the larvae of bee-flies and 
blister-beetles with curiously adapted and specialized life history 
and transformations. 
Again, one may frequently see in midsummer, flying about 
Locusts or perched nearby and sharply watching them, short, 
thickset, grayish flies, somewhat resembling large house-flies. 
These are parasitic Tachina flies. When the Locust essays 
flight, its enemj'^, the fly, darts after it and strives to fasten an 
egg on its neck or at the base of the wing. If successful, a maggot 
shortlj^ hatches therefrom, penetrates the bodj^ of the Locust, 
and there feeds upon and destroys it. 
Young Locusts are the prey of many carnivorous insects, not- 
abh^ the swift-running ground- and tiger-beetles in both larval 
