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.) 



