SB 

 818 

 C578 

 ENT 



!0. 77. 



nited States Department of Agriculture, 



BUREAU OF ENTOMOLOGY, 

 L. O. HOWARD, Entomologist and Chief of Bureau. 



HARVEST 3IITES, OR "CHIGGERS." 



By F. H. Chittenden, 

 Entomologist in ('luin/e of Breeding E.rj/eriments. 



Residents of the South and of the more southern portion of many of 

 the Central States, and especially visitors to these sections, are often 

 subject to great annoyance due to the attacks of minute creatures popu- 

 larly known as " chiggers''^ and ''• red bugs," and, incorrectly, as ticks. 

 These pests are the larval or six-legged 

 forms of harvest mites of the genus 

 Trombidium, the adults of which have 

 eight legs. They are troublesome be- 

 cause of their unpleasant habit of bur- 

 rowing under the skin of human beings. 

 This habit is not normal, and as a con- 

 sequence the mites die, and their pres- 

 ence under the epidermis gives rise to 

 iri'itatiou and inflammation of varying 

 n tensit3^ 



For present purposes we may consider 

 the harvest mites as a class. In figures 

 1 and 2 illustrations of some common 



forms are furnished. The larval harvest mites are of microscopic size, 

 l>lood red, and shaped somewhat like a common tick, being nearly as 

 ])road in front as behind. They belong to the order Acarina and are 

 not true insects (Hexapoda), but are members of a distinct class 

 (Arachnida) along with ticks, spiders, and the like. The parent mites 

 are predaceous on true insects. As early as 1834 Mr. A. L. Duges^ 

 made observations on these mites, which, as previously stated, have six 

 legs in the immature or parasitic stage, while the adults have eight. 

 The adults are of different shades of red and are quite visible. Many 

 persons are familiar with the appearance of the }' oung of certain species, 



'The name "chigger" or "jigger" is evidently a corruption of chigoe, the 

 pernicious sand-flea {Sarcopsi/Ua penetrans L. ) of tropical America, a true flea, 

 which crawls under the toe nails of man, producing })airiful sores which may result 

 seriously if neglected. 



■^Annales des Sciences Naturelles, Vol. I, ser. 1, p. 36; see also P. .Mcgnin, 1. c. 

 Vol. IV, ser. 6, pp. 4-20, 1876, and Murray's Aptera, pp. 129-133. 



2226— No. 77—07 



Troiubiditnn: Larva, higlily mag- 

 nified (from Banks). 



