•HIE MTRIAEODA OF NORTH AMERICA. 



147 



Fam. II. I/I THOBIID M, Newport* 



Scuta 15, insequalia. Pedum posteriorum coxx cxeavationibus in facie depressa. Antennas elongates, setaoese. 

 Ocelli numerosi vel pauces. 



Scuta 15, unequal. Coxa of the last pair of feet witli impressions on a depressed surface. Antenna elongate, 

 setaceous. Ocelli numerous or few. 



'Hie Lithobiidic have the head large and well armed. The antennas setaceous, elongate. 

 The eyes stemmatous. In two of the genera, they are small and numerous, but in the 

 third large and but two in number. The mandibular teeth are strong, very acute, and 

 probably provided with a poison-gland at their base, although it lias never been anatomi- 

 cally demonstrated in this family, that I am aware of. The scuta are of two lands, a, 

 large one alternating with a small one. The females have the anal segment somewhat 

 elongate interiorly, and provided with a pair of forceps on eacli side. In the males these 

 are replaced by a pair of minute styliform appendages. The posterior coxae have a plain 

 depressed surface with indentations, or, as I have called them, excavations on it. I 

 have never seen a specimen of the type of the genus Lithobius ; but Mr. Newport says, 

 that in all his specimens of the family the lai'ger depressed surface is a deep elongate oval, 

 whilst the smaller excavations are transverse, oval, and furrow-like. There is, among the 

 American species of the Lithobiidse, a group in which the larger surface is scarcely de- 

 pressed, with the smaller excavations round and almost punctiform. This I have indi- 

 cated as a distinct genus, with the name of Bothropolys. 



The specific characters of the Lithobiidac are derived from the number of ocelli, the 

 shape of the dental lamina with the number of teeth, the shape, color, and structure of 

 the scuta, &c. The number of the eyes in the adult is fixed within certain limits for each 

 species. But when the young Lithobiid emerges from the egg, it possesses but a single 

 pair of eyes, besides wanting some of its segments. In the genus Henicops (not yet dis- 

 covered in this country), the single pair of ocelli remain as a permanent character; but in 

 the other genera the number of eyes are gradually increased until adult life. Mr. New- 

 port seems to think the number of labial teeth a good specific character, but I have found 

 it to vary considerably. 



* Linn. Trans, xix, p. 275. 



