9 FARMERS’ BULLETIN 671. 
tion from the nails or other outside sources. . Children, and especially 
those who begin to go barefoot in grassy places in June to September, 
are great sufferers from this minute enemy. 
WHAT “CHIGGERS” ARE. 
These pests are the laryal or six-legged forms of harvest mites of the 
genus Trombidium, the adults of which have eight legs. 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, blood red, and shaped 
somewhat like a common tick, being nearly as broad in front as be- 
hind. They belong to the order Acarina and are not true insects (Hex- 
apoda), 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. Dugés! 
made observations on 
these mites, which, 
as previously stated, 
have six legs in the 
immature or para- 
sitic stage, while the 
Fia. 2—Leptus americanus at left; Lepius irritans at right. Highly adultshave eight. The 
magnified, dots under anal extremity indicating natural size. adults are of different 
(After Riley.) 
shades of red and are 
quite visible. Many persons are familiar with the appearance of 
the young of certain species, as they occur on the under surface of 
the bodies of grasshoppers and harvest spiders or ‘‘daddy-long- 
legs” (Phalangiide) and under the wings of the house fly. Just 
what species of harvest mites are troublesome to man in the United 
States is not known, but one of them, perhaps the commonest, is 
referred to in literature as ‘‘Leptus” irritans Riley.” 
SYMPTOMS AND MANNER OF ATTACK. 
Soon after the harvest mite burrows under the human skin a small 
red spot appears (evidently the mite itself gorged with human blood), 
1 Dugés, Ant. Recherches sur l’ordre des Acariens en general et la famille des Trombidiés en particulier. 
In Ann. Sci. Nat. Zool., t. 1, ser. 2, art. 1, p. 36, 1834; see also Megnin, P., Memoire sur les Metamorposes des 
Acariens en general et en particulier sur celles des Trombidions. L.c., t. 4, sér. 6, art. 5, p. 1-20. 1876; and 
Murray, Andrew, Economic Entomology, Aptera, p. 129-133, London, 1877. 
2 Riley, C. VY. Poisonous insects, p. 745, fig. 2980, New York. 1887. (Extracted from Reference Hand- 
book of the Medical Sciences, v. 5.) 
Leptus is a genus founded on the larval Trombidium. Those who may desire further information in 
regard to the structure of theaadult may consult Banks, Nathan: ‘A treatise on the Acarina, or mites.’? 
(In Proc. U. S. Nat. Mus., v. 28, p. 30, 31, 1904.) 
