CHIGGERS — FARRELL 87 



In 1905 Berlese described Tromhicula minor, a mite generally 

 accepted to be a nymph with a body shaped like the figure 8. 

 The monotypic genus Tromhicula was erected for it in the family 

 Trombidiidae. In 1912 Oudemans published a taxonomic sum- 

 mary of chiggers with descriptions and notes on all known 

 species. He included these larvae in the genus Microtrombidium 

 Haller, 1882, type species M. purjnireum Haller, 1882, or in sev- 

 eral genera he himself had created in 1910 and 1911. These genera 

 also were in the Trombidiidae. 



In 1916 the first successful rearing of nymphs from engorged 

 chiggers occurred. In that year Kneissl reported rearing nymphs 

 of the European pest chigger Microtrombidium aidumTialis 

 (Shaw, 1790) . He observed they were shaped not like Microtrom- 

 bidium but had the same form as Tromhicula. He changed the 

 name to Tromhicula autumnalis. In 1917 Miyajima and Okumura 

 made similar observations and changes with Tromhicula akamushi 

 (Brumpt, 1910) . Later, other chiggers which had not been reared 

 to nymphs were moved from Microtrombidium to Tromhicula by 

 various workers. 



Ewing (1929d) established the subfamily Trombiculinae for 

 the vertebrate-infesting chiggers, separating them from the 

 arthropod-infesting mites of the family. 



Willmann, in 1941, published the results of his examination of 

 the type specimen of Tromhicula minor. He determined it to be 

 an adult female, not a nymph. However, this discovery had no 

 effect on the classification. By this time adults of other species 

 had been reared. These adults from cultures were congeneric 

 with T. minor. 



Ewing (1944a) proposed the new family Trombiculidae with 

 two subfamilies, Trombiculinae and Hemitrombiculinae. Womers- 

 ley (1944) added the subfamily Leeuwenhoekiinae and in 1945 

 raised the group to full family status. Ewing (1946a) retained 

 Leeuwenhoekiinae as a subfamily and added the Walchiinae. 

 Wharton (1947b) agreed with Ewing's determinations, added the 

 subfamily Apoloniinae, and redefined the family on the basis of 

 larval characteristics. In his new definition Wharton excluded 

 the subfamily Hemitrombiculinae, which Ewing (1949) has said 

 could well be made a separate family. At the same time Wharton 

 gave a new diagnosis to the subfamilies based chiefly on the num- 

 ber of segments in the larval legs. With this development the 

 classification of chiggers took on its present form at these inter- 

 mediate levels. Wharton, Jenkins, et al. (1951) published a key 



