PEDICULOIDES 



489 



Genus. Pediculoides. 

 Pediculoides ventricosus, Newport, 1850. 



Syn.: Heteropus ventricosus, Newport, 1850; Acarus tritici, Lagreze-Fossot, 

 1851; Physogaster larvarum, Lichtenstein, 1868; Spharogyna ventricosa, Laboul- 

 bene and Megnin, 1885. 



Males are oval in shape, 0*12 mm. in length and 0*08 mm. in 

 breadth, flattened. There are six pairs of chitinous hairs on the 

 dorsal surface and a lyre-shaped lamella on the posterior part. The 

 female in the non-gravid state is cylindrical in form, 0*2 -mm. in 

 length and 0*07 mm. in breadth ; when gravid the posterior part of 

 the body becomes enlarged into a ball, which may attain 1-5 mm. in 

 size, as in the case of Pulex penetrans and of the female Termites. 

 On emerging the young are already provided with four pairs of legs 

 and copulate soon after birth. 



FIG. 353. Pediculoides ventricosus. a, male ; l>, young female ; c , gravid female. 

 Enlarged. (After Laboulbene and Megnin.) 



These animals live on tbe stalks of cereals, and feed on vegetable and animal 

 juices ; they are also found on corn-infesting insects. They invade the barns and 

 seek out the insects living in the dry grains of corn, or wait for an opportunity of 

 obtaining food. They have been repeatedly observed on human beings, particularly 

 labourers occupied in handling grain ; their bite causes severe irritation, local 

 elevation and reddening of the epidermis, as well as fever. It cannot be positively 

 asserted that all cases of the occurrence of cereal mites on man relate to P. ventricosus, 

 as the descriptions are often insufficient. Geber states that one form is Chrithoptes 

 monunguiculosus, or Acarus hordei ; Flemming mentions Tarsonemus uncinatus ; 

 Roller Oribates sp. ; and Karpelles Tarsonemus intectus. 



[The pregnant female Pediculoides has a large round inflated abdomen, in 

 which the ova hatch and the young mature. Later they escape from the parent as 

 adults. F. V. T.] 



