INSECTA. 



301 





The species of this genus occur only in man and some mammals, 

 whose blood they suck. Their motion is sluggish. 



The louse of the human head has been investigated anatomically 

 by our SWAMMERDAM. The intestinal canal is straight, with a large 

 stomach ; there are four vessels secreting urine. Each ovary con- 

 sists of five tubes. The nervous system consists, besides the cere- 

 bral ganglion, of three large ganglia in the thorax, so closely placed 

 behind each other as to touch ; from these ganglia the nerves of the 

 feet arise, and from the last ganglion arise in addition six nerves 

 which are distributed through the cavity of the abdomen. 



See SWAMMEKDAM Bijlel der natuur. bl. 63 86. Tab. i. n. 1 



Sub-genera Phthirus, Hcematopinus, Pediculus LEACH. 



Sp. Pediculus humanus capitis, Pediculus cervicalis LEACH, DE GEER Ins. 

 VII. Tab. i. fig. 6, DUMERIL Consid. gen. s. 1. Ins. PL 53, figs, i, 2, 

 GUERIN Icon. Ins. PI. 2, fig. 5. (Comp. also SWAMMEKDAM, and a gigantic 

 figure twenty inches long by HOOKE Micrograph. Tab. 35). The larger 

 species, considered by LINNAEUS as a variety, which lives upon the body 

 and amongst the garments, differs by the less deep incisures in the side of 

 the abdomen at each ring, by a thorax broader behind, and, as GUERIN has 

 remarked, by longer antennae. Pediculus humanus corporis DE GEEK, 

 Ins. 1. 1. fig. 5, (Pediculus humanus LEACH, Pediculus vestimenti BURM.) 

 As a third parasitic species of man may be added Pediculis pubis L., 

 Phthirus inguinalis LEACH, REDI Exper. circa generationem Insectorum, Ani- 

 stelodani, 1688, I2mo, Tab. 12, fig. superior, GUERIN op. cit. fig. 17. 



Family VI. Mallopfiaga. Mouth supplied with mandibles 

 and maxillse. Tarsi biarticulate, with a single claw or with two. 



On Mammalia, and especially on Birds, different parasitic Insects 

 are found, which were placed by LINNAEUS in the genus Pediculus, 

 but which differ from it by the presence of jaws on the under 

 surface of the head. DE GEER, who discovered this character, 

 justly held it to be so important and essential, that he placed these 

 animals in a distinct genus, to which he gave the name of JRicinus 



1 LEEUWENHOECK investigated the male louse (which is rarer and was unknown 

 to SWAMMERDAM, op. cit. bl. 83) ; he found two testes on each side of the body. 

 This and other remarkable peculiarities in Pediculus hum. corporis are found in 

 LEEUWENHOECK, sesde Vervolg. der Brieven. Delft, 1697, pSste Missive, pp. 187 217. 

 See also Vierde Vervolg. der Brieven 1694, 77ste Missive, pp. 587 591, where the 

 head is described and figured. The horny sheath of the penis L. described as a sting 

 at the posterior part of the body. 



