106 



REPORT 10§^ U. S. DEPARTMEXT OF AGRICULTURE. 



Fig. 21S.— Tarsoncmus pallidus 

 t ration.) 



(Author's illus- 



In 1850 Newport gave the name Heteropus ventricosus (fig. 214) to a mite found on 



the larva of a wasp. Since then similar mites have been found on various insects. 



both alive and dead. The generic name was preoccupied, and was changed to Ped- 



iculoides^ by Targioni-Tozzetti in 1875. The species has become of much economic 



importance, since it is frequently para- 

 sitic upon injurious insects. The abdo- 

 men of the pregnant female (fig. 216) 

 swells to an enormous size, this being 

 due to the development of the eggs. 

 These not only hatch within the parent, 

 but obtain their entire development there, 

 and issue as sexually mature males and 

 females. These may wander about for a 

 time on the body of the mother and soon 

 pair. The body of the male (fig. 215) 

 ends in a broad sucker, wherein is situ- 

 ated the penis. The tip of the female is 

 grasped by this sucker. P. ventricosus 

 Newp. occurs commonly in this country, 

 and another species has been found on the 

 larvae of scolytid beetles. Prof. Herrera, 

 the Mexican entomologist, endeavored 

 without success to breed a Mexican spe- 

 cies to kill the grubs of the cotton-boll 

 weeAT.1. Some species with a more dis- 

 tinctly segmented body and with short 

 legs have been placed by Renter in a 

 new genus — Pediculopsis. One species, P. 



dianthophilus Wolcott, is a serious pest to carnations, and the principal agent in the 



distribution of the "bud-rot" of these plants. The mites burrow down inside the 



buds to feed on the tender tissues within and, going from bud to bud, carry the 



spores of a fungus which produces the rot. In this species the gravid female is 



egg shaped and not spherical. It is closely related 



and possibly identical with the P. 'graminum Renter 



of northern Europe, which occurs on grasses and is 



said to be one of the causes of "silver top." Some 



species of Pediculoides commonly attack the injurious 



insects of grain, as the grain moth, Isosoma, Meromyza, 



etc. Thus it happens that if grain infested with these 



insects, upon wliich there are numerous Pediculoides, 



is used while fresh for straw, the mites, finding their 



natural food drying up, must leave the insects and 



hunt for other food. If this fresh straw is used, as is 



often the case, for mattresses, the mites crawling 



through the ticking, attack the sleeping person, and 



cause innumerable pustules whose intolerable itching 



induces scratching and consequent sores. This der- 

 matitis was for many years a puzzle to pliysicians, 



but was connected with the mite by Dr. Goldberger, 



and Prof. Webster ^ has brought together a considerable 



number of cases where Pediculoides has been troublesome. So minute are these mites 



that they are practically invisible, and tlie disease caused by them was sometimes 



attributed to the injurious insects of the grain. 



^Lah Filippi, 1865, is older, but this name is fortunately preoccupied by Ilagen in 1S53. 

 2 Webster, F. M. A Predacoous Mite Troves Noxious to Man. (Pediculoides ventricosus Newport.) 

 U. S. Dcpt. Agr., Bur. Ent., Giro, lis, 24 p., 13 fig., Apr. 23, 1910. 



Fig. 210.— Tarsonemus latus: Fe- 

 male. (Author's illustration.) 



