BULLETIN 553, U. S. DEPARTMENT OF AGRICULTURE. 



Table II — Actual time taken by the mite (Dermanyssus gallinae) in experiment to go 



through life cycle. 



Date. 



Aug. 



Hour. 



Day. 



/9p.m... 



1 i 



19 a.m... 





/9p.m... 

 \9 a. m... 



} 2 



/9p.m... 

 \9 a. m... 



} 3 



/9p.m... 

 \9a. m... 



I 4 



/9p.m... 

 \9 a. m... 



I 5 



/9 p.m... 

 \9a. m... 



I 6 



/9p.m... 

 \9 a. m... 



} 7 



/9p.m... 

 \9a.m... 



I 8 





/9p.m... 

 \9 a. m... 



I 9 





/9p.m... 

 \9a. m... 



} 10 



9p. m... 



11 



Stage of deve'opment. 



/First-stage nymphs fed on fowl. 

 \ First-stage nymphs are all fed. 



Second-stage nymphs molted from first-stage nymphs. 



/Second-stage nymphs fed on fowl. 

 \Second-stage nymphs recovered fully fed. 



Adults have molted from second-stage nymphs. 



/Females fed on fowl. 



\ Females fully fed recovered. 



Eggs being deposited. 



/Some eggs still being deposited. 



\Some eggs have begun to hatch to larvae. 



Larvae have begun to molt to first-stage nymphs. 



Table III — Probable time in nature the mite (Dermanyssus gallinae) takes to go through 



life cycle. 



Day. 



Hour. 



Stage of development. 



fa; i 



IP-: 



ft 



First 



Second... 

 Third.... 

 Fourth... 



Fifth 



Sixth.... 

 Seventh.. 



Ninth a. m 



Eggs laid. 



fa. m | Eggs hatched to larvae . 



/a.i 



\p.m 1 



/a. m ' Larvae molt to first-stage nymphs. 



\p. m First-stage nymphs feed. 



m 



First-stage nymphs are molted to second-stage nymphs. 



Second-stage nymphs feed. 



Second-stage nymphs molt to adults. 



Females feed. 

 Eggs laid. 



The average rate of deposition is about four eggs per day; that 

 is, one egg in about 6.4 hours. 



The rapidity with which the mite may reproduce is amazing. The 

 possible progeny of one female in five weeks is conservatively esti- 

 mated at 1,631 individuals, or, considering the duration of life of a 

 female as eight weeks, her progeny would total 2,609 mites. 



LONGEVITY. 



As might be expected, since it feeds often and ordinarily does not 

 have to wait long for a host, as do many of the ticks, the mite lives 

 a comparatively short time in the absence of food. The experiments 

 indicate that a certain amount of moisture and moderate temperature 

 favor longevity, while extreme dryness and high temperatures are 

 unfavorable factors. The mites die off much faster in the absence 

 of food during the hot summer months than they do during the 



