Trombidiformes 167 



with a small central vesicle, which marks the seat of the puncture. The 

 blanched area is surrounded by a rosy red areole. The lesions may 

 itch severely, especially when warm in bed, or when the body is heated 

 by exertion. Rubbing and scratching usually break the central vesicle 

 and the possibility of secondary infection then arises. Itching usually 

 subsides in two to three days, but the marks may last longer." Web- 

 ster 1910 states that some severe cases show general systemic symp- 

 toms such as a "rise of temperature from 99° to 102°; in one case the 

 temperature rose to 103.8°; the pulse rate is accelerated to 100, or as 

 high as 110 — in one case to 130. Other symptoms were intense head- 

 ache, anorexia, nausea, in some cases vomiting, and a mild form of 

 diarrhoea. In severe cases some complained of general joint pains and 

 backache; in these the urine was examined and albumin in small 

 amount was found, but no casts or blood. When the acute symptoms 

 disappeared so did the albumin." Asthma due to these mites has also 

 been reported. Generally, the mite is not considered important in con- 

 trolling insect pests, although in isolated cases or in the laboratory, 

 colonies of larvae may be completely eradicated by this mite. The dis- 

 tribution of this species appears to be world-wide. Until recently only 

 one species, Pyemotes {— Pediculoides) ventricosus, was recognized 

 but Oudemans 1937 has described several more. 



Siteroptes {— Pediculopsis) graminum (Renter) superficially re- 

 sembles the preceding species, but is a pest of grasses and grains, 

 causing considerable damage to wheat, oats, barley, and rye, as well 

 as being the active agent in the dissemination of the spores of the car- 

 nation bud rot, Sporotrichum poae, in the United States. Infested ce- 

 reals may be malformed and stunted, and often silvered, leading to 

 the common name of "silver top." 



References: 



Cooper, K. W. 1937. Reproductive behaviour and haploid parthenogenesis 



in the grass mite, Pediculopsis graminum (Reut.) (Acarina, Tarso- 



nemidae). Proc. Natl. Acad. Sci. 23(2):41-44. 

 . 1940. Relations of Pediculopsis graminum and Fusarium poae to 



central bud rot of carnation. Phytopathology 30(10) :853-859. 

 Herfs, A. 1926. Okologische Untersuchungen an Pediculoides ventricosus 



(Newp.). Berl. Zoologica, Heft 74, Stuttgart. 

 Jacot, A. P. 1936. An undescribed mite from the southern Appalachians. 



Canad. Ent. 68(4):82-85. 

 Oudemans, A. C. 1937. Tijdschr. v. Ent. 80, Verslag IV-VIII. 



