CraCGERS — ^FARRELL 99 



duce inflamed spots. It is an unnatural situation for the mites and 

 they soon die." Howard (1918) said that chiggers do not bury 

 themselves when engorging but insert mouthparts and fill with 

 blood, and after engorging fall off. 



Ewing (1921) gave an account of early investigations on 

 geographic and seasonal distribution, habitat preference, manner 

 of attaching to human skin, and related topics. The normal hosts 

 were not known. Ewing tried to find chiggers feeding on plants, 

 although he did not believe they used plant food. His efforts to 

 find them on insects and small mammals failed also. He found 

 many attached to a shed snakeskin from which they were unable 

 to free themselves, and he concluded snakes were not normal 

 hosts. He described and figured chiggers attached to the surface 

 of human skin, and said they fed on lymph of the "true skin." 

 Miller (1925a and 1925b) showed snakes to be normal hosts. 

 Ewing (1926a) found the Carolina terrapin to be an important 

 host; and later he (1929b) added the rabbit and several species 

 of birds to the list. 



Keay (1937), clearly making a study of the ecology of Trom- 

 bicula autumnalis, determined something of its seasonal distribu- 

 tion and host preferences. She found its local distribution 

 sporadic but was unable to determine limiting factors in vegeta- 

 tion or soil, although most records were from calcareous soil. 

 Buxton (1945) made similar comments on the natural history of 

 this species. 



In 1943, Acomatacartis paradoxa (Andre) Brennan, 1949, was 

 described from scorpion, an exception to Swing's ecological 

 diagnosis of the family Trombiculidae. 



Much information has been assembled by the groups working 

 with scrub typhus. Blake, Maxcy, et al. (1945) gave an account 

 of the habits of free and attached chiggers, the results of studying 

 several species in New Guinea. Mackie, Davis, et al. (1946), in 

 Assam and Burma, found some evidence of seasonal activity of 

 the mites in relation to rains by using the number of cases of 

 the disease as an index. Audy (1947a) pointed out the localized 

 distribution of T. delieTisis Walch, 1922, could have been the 

 result of ecological demands by the free-living stages. He stated 

 the mites were not conspicuous around the burrows of their rat 

 hosts but were most abundant in "fringe habitats," the inter- 

 mediate areas between forest and open scrub. During dry seasons 

 he found the chiggers only in moist areas, but the populations 

 increased greatly after the onset of the rains. Audy (1947b) 

 reemphasized the peak incidence of T. deliensis larvae during the 



