A PREDACEOUS AND SUPPOSEDLY BENEFICIAL MITE, 

 PEDICULOIDES, BECOMES NOXIOUS TO MAN. 



By F. M. Webster, 

 Bureau of Entomology, Washington, D. C. 



Introduction. 



Attacks of mites upon humans are by no means new, various 

 instances of this character having been observed in Europe and 

 recorded in various EngHsh and Continental publications both 

 entomological and medical. In this country, up to very recently, 

 except in the case of the itch mite, Sarcoptides psoriques Alegn., 

 these have all been grouped under the name "chigger," which is 

 evidently a corruption of "chigoe," a tropical species, Sarcopsylla 

 penetrans L., which is not a mite at all, but a flea. Thus it has 

 come about that people walking during summer in grassy or 

 weedy places or in woodlands are very often attacked by "chig- 

 gers" and suffer serious inconvenience and much pain on account 

 of attacks of what are probably the larvae of several species of 

 mites ; notably the Trombidiums, just which one or how many is 

 not at present known. 



The mite involved in the two epidemics of dermatitis in the 

 United States, to which this paper especially relates, is quite 

 certainly the same as the one discovered by myself in 1882 and 

 determined for me by Mons. Jules Lichtenstein of Montpellier, 

 France, as Heteropus ventricosiis, Plate III, figs. 1,3, and since 

 known in this country as Pediculoides ventricosus Newport. 

 Huber has since made this species a synonym of Pediculoides 

 tritici Lagreze-Fossat, to which Moniez credits a large number 

 of instances of mites attacking man in Europe. 



MITES ATTACKING MAN IN EUROPE AND OTHER COUNTRIES. 



In a publication relating to parasitology, both animal and 

 vegetable, by R. Moniez,^ quite a number of recorded instances 

 have been brought together, some of them it is quite probable, 

 involving the species to which this paper relates. Moniez is, 

 however, vague and indefinite, and while crediting a large num- 

 ber of attacks of mites upon man to Pedicidoides tritici, the fol- 



1. Traite de Parasitologi Animale et Vegetal, Applique a la Medicine, 

 Paris, 1896. 



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