10 
THE COLORADO EXPERIMENT STATION 
CHIGGER, Trombidium holosericeum 
DESCRIPTION.—The chigger is a very small mite, as shown by the 
mark by the side of Fig. 10. The body, oval in shape, is provided, in the 
adult state, \vit*h four pairs of legs. The terminal end of the leg is provided 
with two hooklets which enable it to hold to objects and to move about 
easily. It is provided with conical shaped mouth parts illustrated in Fig. 10. 
LIFE HISTORY.—The mites lay their eggs in cracks and crevices and 
filth of the hen houses. The eggs hatch in a few days, if conditions are favor¬ 
able, and multiply very rapidly in the hotter months of summer, July and 
August. 
CONDITIONS PRODUCED.—By means of its mouth parts the mite 
wounds the skin and sucks blood. When engorged it is blue to red color, due 
to the blood taken into its digestive tract. During the summer of 1911, the 
writer studied one flock of chickens in which the infested birds showed symp¬ 
toms similar to birds infested by lice. The hosts became unthrifty and ceased 
laying and the setting hens with feathers ruffled, deserted their nests and 
many died. Many were found dead under the roosts in the mornings. Exam¬ 
ination of the nests, roosts and the birds revealed millions of the parasites. 
This was in the month of August. 
TREATMENT.—Give the same treatment as for lice. Absolute clean¬ 
liness, and plenty of kerosene on the roosts and air slaked lime on floors and 
in nests is essential. 
Figure 10. —The chicken chigger, Trombidium holosericeum. ventral view. a, 
mouth parts; b. palpi; c, hooklets on the free extremity of leg, with which the 
mite holds on; d, uterus .filled with eggs. The small mark to the right indicates its 
natural size. 
Figure 11.—The chicken flea, Pulex avium, a, antennae; b, stylette with 
which it wounds the skin; c, hooklets on free end of legs. Note the stout legs 
which give the flea great power to jump. 
