Histiogaster (entomophagus?) spermaticus, Trouessart, 1900.
The genus Histiogaster, which also approaches the Tyroglyphinæ, is characterized by the circumstance that the males possess suctorial pores used in copulation, as well as leaf-shaped appendages at the posterior end of the body. They feed on vegetables, especially on small fungi.
Fig. 366.—Histiogaster (entomophagus?) spermaticus: on left, male; on right, female—both from the abdominal aspect. 200/1. (After E. Trouessart.)
This species has been described by Trouessart,[352] who found numerous specimens, some adult, others in the developmental stage (larvæ, nymphs), and ova, in the fluid removed by puncture from a cyst of the right testis. The males measure 0·25 mm., the females 0·32 mm., and the larvæ 0·1 mm. in length. The author is of opinion that the animal—perhaps a fertilized female—was introduced by a catheter, and, as a matter of fact, it was afterwards found that the patient had once had the catheter passed in India while suffering from pernicious fever.
It would here rather appear to be the case of a facultative parasitism of an otherwise free-living species. Histiogaster entomophagus, Laboulbène, is found occasionally in collections of insects feeding on larger species containing much fat; the species also occurs on dry cantharides; it appears to belong to the region of South Europe, where, however, it is widely spread.
[Entomophagus occurs all over Europe and in America. It has been described under the following names: Acarus malus, Shimer, 1868 (Trans. Illinois Hort. Soc.); Dermaleichus mali, Riley, 1873 (Rep. Ins. Missouri, v, p. 87); Tyroglyphus mali, Murray, 1877 (“Eco. Ent. Apt.,” p. 275); T. corticalis, Michael, 1885 (Trans. Roy. Micros. Soc., ser. 2, v, 3, p. 27, figs. 1 to 14); Histiogaster corticalis, Canestrini, 1888 (Prosp. Acarof., iii, p. 397); H. aleurophagus, Sicherin, 1894, Canestrini, Prosp. Acarof., vi, p. 815. Trouessart’s species is evidently distinct.—F. V. T.]
Genus. Cheyletus.
Cheyletus mericourti, Lab.