Successful Feeding Experiments with an Adult Trombiculid Mite (Order Acarina)

Abstract

ALTHOUGH certain species of Trombiculid mites belonging to the sub-family Trombiculinae have long been suspected of being the carriers of tsutsugamushi disease, now more commonly referred to as scrub typhus, it is only recently that Blake et al.1 have demonstrated the presence of Rickettsia orientalis in Trombicula fletcheri Womersley and Heaslip. In their paper., which contains a valuable review of the literature on scrub typhus, they say that "existing knowledge regarding the life-history, habits and bionomics of trombiculid mites is quite inadequate in view of their importance as disease vectors and pests of man". This is particularly true of the feeding habits of the nymphal and adult stages. Miyajima and Okumura2, who first established Trombicula akamushi (Brumpt) as the vector of tsutsugamushi fever in Japan, say that "in nature the nymph and adult seem to live on the juice of plants". Womersley and Heaslip3, too, appear to believe that the adults are probably vegetarian. Banks4, on the other hand, makes a general statement to the effect that the mature mites feed on small insects, and mentions particularly plant lice, young caterpillars and grasshopper eggs. But l*e gives no details of any observations on the subject. Blake et al. (loc. cit.), in summing-up our present knowledge of the feeding habits of the nymphal and adult stages, say that "the food of these stages is variously reported to include plant juices, decaying organic matter and insect excrement". It would appear., therefore, that though adults have occasionally been reared in the laboratory there are few, if any, definite records on their feeding habits. Indeed it would seem doubtful whether they have actually been observed in the act of feeding.