CHIGGERS — FARRELL 159 



a dissected ovary in the culture. Later the nymph located the 

 ovary and fed for 15 to 20 minutes. It changed its position twice 

 during feeding. Flowing movements were observed in the fluid 

 mass of the ovary immediately in front of the nymph's gnatho- 

 soma. Bubbles or fluid materials of varying densities were ob- 

 served moving posteriorly through the middle of the gnathosoma. 

 Observations on the other three acts were similar, but in two of 

 these the mass of the ovary was pushed up to a nymph puttering 

 in the region of a needle scratch. On one other occasion a nymph 

 inserted its gnathosoma into the mass of a dissected ovary and 

 remained in position for about a minute. No signs of feeding could 

 be determined. It disengaged its gnathosoma and lay on its side 

 while seeming to clean its appendages. On a number of other 

 occasions nymphs ignored dissected Acdes ovaries. 



One culture was established with two nymphs obtained from 

 larvae engorged on a white mouse in the laboratory. Vermiculite 

 was used as a medium through which the mites could move. 

 Sinella curviseta, a collembolan, was maintained in this culture. 

 These insects laid eggs and reproduced. When the culture was 

 flooded 163 days after it had been established, one plump, living 

 nymph was recovered. It can be inferred that this nymph fed 

 on som.e stage of Sinella curviseta. This record of 163 days rep- 

 resents also the longest time a nymph was kept alive. 



As indicated in the preceding paragraph, E. peromysci larvae 

 engorged successfully on white mice in the laboratory. The un- 

 engorged larvae were obtained from forest soil materials by 

 means of Berlese funnels. One such experiment was used as a 

 start to obtain information concerning the time involved in vari- 

 ous stages of the life cycle. Numerous wild-caught, unengorged 

 larvae were placed on a white mouse. One engorged chigger was 

 obtained on the fourth day and seven engorged chiggers on the 

 seventh day after exposure. These eight chiggers were preserved. 

 On the eighth day after exposure of the mouse to the larvae, 15 

 engorged chiggers were recovered. These were placed in a special 

 vial. Four days later these chiggers were immobile, entering the 

 nymphochrysalis stage. Nine days after this stage had been 

 reached, one nymph was found in the vial. On the 11th day after 

 the inim.obility of the larvae, the vial contained nine nymphs. No 

 other nymphs or nymphochrysalids were found. These nymphs 

 were held in the special vial without addition of any food. Thirty- 

 six days later the vial contained one dead and eight living nymphs. 



It was demonstrated, also, that E. peromysci would attach to 

 man. Fifteen unattached, unengorged E. peromysci larvae were 



