Posterior coxae laminate; trochanters small.
Labrum concealed; antennae somewhat distant from the eyes, their insertion narrowing the front .......... Eucnemides.
Labrum visible, free; antennae arising near the eyes under the frontal margin .......... Elaterides.
Labrum transverse, connate with the front.
Ventral segments six; claws simple; tibial spurs well developed. .......... Cebrionides.
Ventral segments five; claws serrate; tibial spurs moderate. .......... Perothopides.
Posterior coxae not laminate; trochanters of middle and posterior legs very long ..........Cerophytides.
Fig. 135—Larva of Fornax n. sp. Hawaii. A, Upper side; B, under side: s s, position of spiracles; C, head more enlarged; D, under side of terminal segment; a, anus.
Throscides are considered to be distinguished by the mesosternum being impressed on each side in front for the accommodation of the posterior face of the front coxae. The genus Throscus has the antennae clavate. The classification of the Elaterides and these forms is a matter of the greatest difficulty, and, if the larvae are also considered, becomes even more complex. Cebrionid larvae are different from those of any of the other divisions, and possess laminate, not calliper-like, mandibles. The larvae of Eucnemides (Fig. 135) are very little known, but are highly remarkable, inasmuch as it is very difficult to find any mouth-opening in some of them, and they have no legs. The other divisions possess very few species compared with Elaterides. In Britain we have about sixty species of Elaterides, four of Throscides and three of Eucnemides; Cerophytum was probably a native many years ago. Neither Perothopides nor Cebrionides are represented in our fauna; the former of these two groups consists only of four or five North American species, and the Cerophytides are scarcely more numerous.