10 
THE COLORADO EXPERIMENT STATION 
CHIGGER, Trombidium holosericeum 
DESCRIPTION.—The chigger is a very small mite, as shown by tl 
mark by the side of Fig. 10. The body, oval in shape, is provided, in tl 
adult state, with four pairs of legs. The terminal end of the leg is provide 
with two hooklets which enable it to hold to objects and to move aboi 
easily. It is provided with conical shaped mouth parts illustrated in Fig. 1 
LIFE HISTORY.—The mites lay their eggs in cracks and crevices an 
filth of the hen houses. The eggs hatch in a few days, if conditions are favo 
able, and multiply very rapidly in the hotter months of summer, July ar 
August. 
CONDITIONS PRODUCED.—By means of its mouth parts the mi 
wounds the skin and sucks blood. When engorged it is blue to red color, di 
to the blood taken into its digestive tract. During the summer of 1911, tl 
writer studied one flock of chickens in which the infested birds showed sym; 
toms similar to birds infested by lice. The hosts became unthrifty and cease 
laying and the setting hens with feathers ruffled, deserted their nests ar 
many died. Many were found dead under the roosts in the mornings. Exan 
ination of the nests, roosts and the birds revealed millions of the parasite 
This was in the month of August. 
TREATMENT.—Give the same treatment as for lice. Absolute cleai 
liness, and plenty of kerosene on the roosts and air slaked lime on floors an 
in nests is essential. 
Figure 10. —The chicken chigger, Trombidium holosericeum, ventral view. ; 
mouth parts; b, palpi; c, hooklets on the free extremity of leg, with which th 
mite holds on; d, uterus filled with eggs. The small mark to the right indicates it 
natural size. 
Figure 11.—The chicken flea, Pulex avium, a, antennae; b, stylette wit 
which it wounds the skin; c, hooklets on free end of legs. Note the stout leg 
which give the flea great power to jump. 
