CmCGERS — FARRELL 155 



showed a correlation between seasonal rains and seasonal abun- 

 dance of T. deliensis at Imphal. No literature has been found on 

 physical factors limiting species of Euschongastia. 



Cultures: Sixty-eight cultures of E. peromysci were estab- 

 lished. Usually cultures were started with nymphs which readily 

 metamorphosed from engorged chiggers held in special plaster- 

 charcoal lined vials. In culture the nymphs lived for varying 

 periods of time, but in general the history of the cultures was 

 uniform. The nymphs steadily declined in activity and died. No 

 later developmental stage was obtained. 



Of the variety of culture containers tried, the most satisfactory 

 were made with the bottom intact and a layer of plaster-charcoal 

 poured in. Jars and bottles with bottoms removed and the open- 

 ings plugged with plaster-charcoal were difficult to make and 

 awkward to use. It was necessary to place them in finger bowls to 

 catch the moisture which escaped through the plaster-charcoal. 

 Jars lined with moist cellulose wadding were unsatisfactory. 

 Nymphs in them soon became immobile. Cultures in jars lined 

 completely with plaster-charcoal were more difficult to examine 

 than those in unlined jars, although nymphs lived well in them. 

 Odd containers used for special purposes were difficult to manage 

 and to observe and gave no promise of being better for the mites 

 than more convenient sizes and shapes. Several sorts of con- 

 tainers were useful. The shallow weighing bottles v/ith openings 

 the full diameter of the bottles permitted unobstructed examina- 

 tion with the dissecting microscope. They were used extensively 

 in feeding trials. However, active mites were sometimes crushed 

 between the long, tapered, ground-glass sealing surfaces. Small, 

 4-ounce, wide-mouth jars were satisfactory, but control of mois- 

 ture was more difficult with them than with larger containers. 

 The wide-mouth pint jar seemed best adapted for general use. 

 The chief disadvantage of this jar lay in its being too deep for 

 observation vv^ith the dissecting microscope. This difficulty was 

 removed when the layer of plaster-charcoal was made sufficiently 

 thick. Also, the extra absorbent material m.ade control of mois- 

 ture less critical. Solid metal lids and screw bands regularly 

 supplied with the jars were found to be the most satisfactory 

 covers for the cultures. Wide-mouth pint jars about one-third 

 filled with plaster-charcoal and fitted with the solid lids made 

 compact and useful units. 



Nymphs were placed in culture jars without adding a material 

 through which they could move when experiments to find an 

 acceptable food were being carried out. When given the oppor- 

 tunity, the mites would quickly enter soil or any loose medium 



