CHIGGERS — FARRELL 105 



cultures which were reproducing. They were placed, also, in a 

 jar with soil in which a deer mouse, infested with mites and fleas, 

 was kept. Sinella curviseta Brooks, a collembolan, from Mr. 

 Louis Lipovsky, University of Kansas, was maintained in many 

 later cultures. Onychiurns sp. and .S'. curviseta, fed on Brewer's 

 yeast powder, reproduced in cultures, laying numerous spheri- 

 cal eggs. 



j\Iost cultures were kept in a darkened cabinet at room con- 

 ditions. Three were held in an incubator at 30° C, three were 

 kept at 5° to 7.5° C, and one at 10 to 15° C. 



To start cultures, engorged larvae usually were held in special 

 vials until they had transformed into nymphs. The vials were 

 flooded with distilled vrater. The nymphs floated to the top and 

 were transferred by needle into culture jars. Most cultures were 

 inspected at daily to v/eekly intervals, and food v/as offered. 

 Distilled water was added, as judged necessary. When cultures 

 were discontinued the jars were flooded with tap water. Dead 

 nymplis were recovered and preserved. Living nymphs were pre- 

 served or transferred to other cultures. Identity of nymphs in 

 most cultures was determined by sampling the lot of chiggers 

 from which the nymphs were obtained. 



A few living chiggers were used to obtain nymphs of known 

 species. For these determinations, each engorged chigger was 

 placed in a separate special vial. When it had metamorphosed into 

 a nymph, the vial was flooded with water. The nymph and the 

 cast larval skin were picked from the surface of the water. The 

 skin v/as mounted on a microscope slide and from it the species 

 of the nymph was determined. 



Unattaclied E. peromysci from soil were placed on three white 

 mice. The hosts v/ere held in small beakers. Chiggers were re- 

 moved by dissecting needle from the water surface in the collect- 

 ing vessels and placed on the fur of the hosts. Hosts were re- 

 tained about three hours in the beakers and then were put in 

 small cages in funnels over water. When the chiggers detached 

 they wei'e collected from the surface of the water. 



A few unattached E. peromysci collected from soil v/ere used 

 to determine if they would attach to man. A small hole about 

 5 mm. in diameter v/as cut in the center of a piece of adhesive 

 tape measuring 50 mm. by 80 mm. A glass ring, 17 mm. by 5 mm., 

 was placed over the hole on the adhesive side. A piece of fine 

 silk, 30 mm. in diameter, was placed on the glass ring and made 

 concave by finger pressure. A drop of distilled water was placed 



