Fam. II. LITHOBIIDÆ, Newport[1]
Scuta 15, inæqualia. Pedum posteriorum coxæ excavationibus in facie depressa. Antennæ elongatæ, setaceæ. Ocelli numerosi vel pauces.
Scuta 15, unequal. Coxa of the last pair of feet with impressions on a depressed surface. Antenna elongate, setaceous. Ocelli numerous or few.
The Lithobiidæ have the head large and well armed. The antennæ 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 has never been anatomically demonstrated in this family, that I am aware of. The scuta are of two kinds, a large one alternating with a small one. The females have the anal segment somewhat elongate inferiorly, and provided with a pair of forceps on each side. In the males these are replaced by a pair of minute styliform appendages. The posterior coxæ 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 larger 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 Lithobiidæ, a group in which the larger surface is scarcely depressed, with the smaller excavations round and almost punctiform. This I have indicated as a distinct genus, with the name of Bothropolys.
The specific characters of the Lithobiidæ 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 discovered 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. Newport 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.
