THE CHICKEN MITE. 
engorged, and is now bright red, owing to the ingested blood showing 
through the skin. The measurements of the mite (average of five) 
at this stage are: Length, 568 microns (abdomen only); width, 
338.4 microns; thickness (average of three), 266 microns. After a 
period of somewhat less than 24 hours the first-stage nymph molts 
to the second stage. The average mean temperature during the 
period when the molting was observed was 82.9° F. 
THE SECOND-STAGE NYMPH. 
The second-stage nymph, like the preceding stage, requires a short 
period of rest to harden the integument. As soon as the nymph 
becomes active it is 
ready to feed. Some 
authors have said that 
the mite takes long 
periods of rest. The 
writer finds that when 
such rest periods are 
taken it is from force 
of circumstances and 
not from desire on the 
part of the mite. The 
mite before feeding 
measures (average of 
four) 538.2 microns in 
length and 297.9 mi- 
crons in width. After 
feeding, the mite meas- 
ures 751.9 microns in 
length by 461.4 microns 
in width (average of 
10). The second-stage 
nymphs molt to adults (fig. 1). This is the rule, although there may 
be some nymphs which undergo an additional molt before reaching 
the adult stage. The writer found one mite which apparently had 
three nymphal stages. A single instance, however, can hardly be 
accepted as sufficient evidence for making an exception to the rule. 
THE ADULT. 
As soon as the males crawl out of their nymphal skin they rest a 
short time, and are then ready to reproduce. They may clasp a 
nymph if no females have yet appeared, but as soon as a female 
appears a male will find her and clasp her, the venter of the female 
in close contact with the venter of the male. It is certain that 
Fig. 1. — The chicken mite (Dermanyssus gallinae) : Fe- 
male mite before engorgement. Greatly enlarged. 
(Bishopp and Wood.) 
