2 BULLETIN 553, U. S. DEPARTMENT OF AGRICULTURE. 



Molting, mating, and deposition took place in tubes or small vials. 

 In case individuals were being watched, vials were used, and where 

 many mites were confined, test tubes were used. The vials were 

 plugged with absorbent cotton covered with a small piece of black 

 cloth. Black cloth was used because, owing to the contrast in color, 

 it was much easier to observe the small white eggs and larvae. The 

 test tubes were plugged with cotton covered with white cheesecloth. 

 No moisture or food of any sort was added to the tubes. 



In the longevity experiments varied conditions were supplied. 

 Some of the mites were kept in tubes on moist sand, others were kept 

 in dry tubes, and others were on roosts. In the longevity experiment, 

 in which the mites were supplied with a hen's egg, the egg was in a 

 lantern chimney, both ends of which were covered with a piece of 

 black cloth. 



LIFE HISTORY. 



THE EGG. 



In appearance the egg of the mite is a small, oval, smooth, pearly 

 white, and somewhat iridescent object (PL I). Ten eggs measured 

 showed a maximum length of 387 microns, a minimum of 373 microns, 

 a maximum width of 265.5 microns, and a minimum width of 244 

 microns, the average length being 379.3 microns and the average 

 width 255.65 microns. 



Incubation during the latter part of August took place in about 

 48 hours. The average mean temperature at this time was 78.43° F. 



THE LARVA. 



The young larva (PI. I) on hatching is white and has only three 

 pairs of legs. At the rear of the abdomen is a small protuberance 

 which does not appear on any other stage. The larva moves about 

 slowly, unlike the other stages, which are very active. The length 

 and width of the larval body measure practically the same as those of 

 the eggs. Without ever having fed, the larva? molt to nymphs. Molt- 

 ing takes place in about 24.5 hours after hatching, when the average 

 mean temperature is 73.5° F. 



THE FIRST-STAGE NYMPH. 



The young nymph (PI. I) backs out of its larval skin like a per- 

 son drawing his hand out of a tight glove. It has now acquired 

 another pair of legs, making four pairs. After a few hours of rest- 

 ing, to give time for the body integument to harden, it becomes very 

 active and will now feed if given a chance. The first-stage nymph is 

 slightly darker in color than the larva, having a brownish tinge. 



With its long, piercing mouth parts the nymph sucks the blood 

 of the fowl. It crawls from the fowl onto the roost when fully 



