FAM. VII.-SILPHIDAE.

Mentum quadrate, sometimes slightly emarginate, frequently with a transverse piece between it and the ligula, which is prominent, emarginate, or bilobed; gular suture distinct.

Maxilla with two lobes, inner one sometimes with a terminal hook.

Eyes finely granulated, sometimes absent.

Antennæ inserted under the margin of the front, behind the base of the mandibles; 11-jointed, rarely 9 or 10-jointed: gradually or suddenly clubbed at the apex, sometimes nearly filiform.

Prothorax with the epimera and episterna not distinct. Mesosternum very short, side pieces attaining the coxæ. Metasternum large, nearly truncate behind; episterna long; epimera large, distinct.

Anterior coxæ large, conical, contiguous; middle coxæ oblique, not prominent, except in Brathinus; posterior contiguous (except in the foreign genus Leptoderus), not extending to the margin of the body, prominent internally, rarely (Clambini) laminate.

Abdomen with six free ventral segments, except in Sphæ rites, which has but five.

Legs sometimes thick, subfossorial (Necrophorus), sometimes very slender (Pteroloma); tibiæ with large terminal spurs, the anterior ones of the male usually dilated; tarsi usually 5-jointed; posterior trochanters prominent, or not.

The anomalous form of the middle coxæ in Brathinus Lec. requires the division into two sub-families:

Middle coxæ oblique, not prominent.

Middle coxæ conical, prominent.

Sub-Family I.-SILPHIDAE (genuini).

SILPHIDE. BRATHINIDE.

This sub-family contains species which live on decomposing animal matter or on fungi; some species of Catops are found only in ants' nests, while the wonderful genus Leptoderus, not yet found in America, lives in caves; it differs remarkably from other genera of the family by the long cylindrical thorax, the globose, connate

elytra, and the widely separated posterior coxæ.

Like nearly all cave insects, it is destitute of eyes. Doubtless, species of this genus remain to reward the scientific explorers of our large west

ern caves.

According to the form of the body, and the position of the posterior trochanters, the following tribes are defined :

Posterior coxæ simple;

Posterior trochanters prominent (body not globose).

Posterior trochanters not prominent (body nearly globose).

Posterior coxæ laminate, covering the legs.

SILPHINI.

ANISOTOMINI.

CLAMBINI.

Tribe I.-SILPHINI.

Body never globose, sometimes elongate, usually oval, or even nearly circular, and then usually with a thin margin of the thorax and elytra extending beyond the body; the antennæ are 11-jointed, but with the second joint in one genus (Necrophorus) almost obsolete; with a globose 4-jointed club in that genus, gradually clubbed in the others, with the eighth joint in some genera smaller than the contiguous ones. Epimera of metathorax not covered by the elytra. Posterior coxæ contiguous, or nearly so; their trochanters prominent internally, frequently emarginate or toothed. Tarsi 5-jointed, except in the female of Adelops, where the anterior ones are only 4-jointed.

This sub-family contains the largest insects of the family; the species of Necrophorus are remarkable for the black elytra, truncate at tip, and ornamented with large red spots. They live on dead animals, and a pair of them will bury the body of a small mammal with wonderful rapidity. Silpha is also easily recognized by the rounded outline and thin margin.

Our genera may be thus arranged, in two sub-tribes:

Abdomen with six visible ventral segments.
Abdomen with five visible ventral segments.

Sub-Tribe 1.-Silphini (genuini).

SILPHINI. SPHÆRITINI.

Nothing general can be stated in regard to the genera of this sub-tribe; which may be divided, according to the position of the head, into two groups.

Head separated from the thorax, movable.

Head immersed in the thorax.

SILPHE.

CATOPES.

Group I.-Silphæ.

Insects of large or moderate size, living on carrion, compose this group. Pteroloma (which includes Lyrosoma Mann.) and Necrophilus occur only in the Pacific district; the other two genera are found on both sides of the continent.

Our genera are:

Antenna with ten apparent joints, club globose, 4-jointed. NECROPHORUS. Antennæ with eleven distinct joints;

Antennæ clubbed,* tibiæ armed with spines;

Third joint of antennæ not longer than the second, shorter than the first.

Third joint of antennæ as long as the first.

Antennæ nearly filiform, tibiæ not spinous.

Group II. Catopes.

SILPHA. NECROPHILUS.

PTEROLOMA.

Insects of small size and usually ovate form; some live on carrion, others in fungi, others in ants' nests. The 8th joint of the antennæ is smaller than the 7th, except in Colon.

Antennæ clubbed;

ADELOPS.

CATOPTRICHUS.

CATOPS.
COLON.

Eighth joint of antennæ small.

Eighth joint of antennæ larger than the seventh.

Catoptrichus Frankenhaueseri, the type and only species known, is found in Sitkha. Adelops hirtus, the only species yet found in the United States, occurs in the Mammoth Cave, Kentucky; the other western caves will yet furnish other species.

Sub-Tribe 2.-Sphæritini.

This sub-tribe contains but a single genus, Sphærites, of which but one species in Europe and another (S. glabratus Mann.) in Russian America are known. The form is oblong oval, convex;

* In Necrophilus tenuicornis. however, the antennæ are as slender as in Pteroloma.

the elytra are strongly truncate, and striate; the antennæ are slightly geniculated, with the first joint much elongated; the club is rounded, composed of three joints. The appearance is very similar to Hister.

This genus has been placed by Redtenbacher in Nitidulidæ, but the form of the anterior coxæ is altogether different, and entirely similar to that seen in the present family, in which it is retained by other systematists. But the difference in the abdomen seems to me to indicate a separate sub-tribe.

Tribe II.-ANISOTOMINI.

Body oval, convex, sometimes hemispherical, sometimes capable of being contracted into a ball. Mandibles with a basal molar tooth. Antennæ 11-jointed, clubbed, the eighth joint frequently smaller than the contiguous ones. Epimera and episterna of metathorax covered by the elytra. Posterior coxæ contiguous; their trochanters not prominent inwardly. Tarsi variable.

This tribe consists of small species, which live either in decomposing fungi, or under the bark of dead trees.

A. Tarsi with the same number of joints in both sexes; body not at all contractile ;

All the tarsi 5-jointed; eighth joint of antennæ small. HYDNOBIUS.*
Anterior and middle tarsi 5-jointed, posterior 4-jointed;

Mesosternum carinate; eighth joint of antennæ small. ANISOTOMA.
Mesosternum flat; eighth joint of antennæ hardly distinct.

CYRTUSA.

Anterior tarsi 5-jointed, middle and posterior 4-jointed; club of antennæ 3-jointed. COLENIS.

B. Tarsi dissimilar in the two sexes; body more or less contractile ;

Club of antennæ 5-jointed, eighth joint small.
Club of antennæ 3-jointed.

LIODES. AGATHIDIUM.

Tribe III.-CLAMBINI.

Body oval, capable of being more or less contracted into a ball. Antennæ 9- or 10-jointed, clubbed. Episterna of metathorax not

I introduce this genus on the authority of Erichson, who referred (Wiegm. Archiv, 1847, ii. 100) to it Liodes alternata Mels., which, however, I find to have only 4-jointed posterior tarsi, and have accordingly placed it in Anisotoma. Nevertheless, it is quite possible that Erichson may have had before him a genuine species of Hydnobius, unknown to me.

covered by the elytra. Posterior coxæ contiguous, dilated into laminæ covering the posterior thighs; trochanters not prominent. This tribe consists of very minute species, living in decomposing vegetable matter. On account of the extreme minuteness of the insects, the generic descriptions have been very imperfect, and indeed inaccurate; it is only in the works of Redtenbacher, Lacordaire, and Duval that the full characters have been detailed. This fact will account for the confusion regarding the genus Sternuchus, established by me in Agassiz's work on Lake Superior, which I afterwards united with Clambus.

Club of antennæ 3-jointed; coxal plates narrow, dilated internally (body glabrous). EMPELUS. Club of antennæ 2-jointed; coxal plates very broad (body usually pubescent); Antennæ 10-jointed; abdomen with 6 ventral segments. CALYPTOMERUS. Antennæ 9-jointed; abdomen apparently with 5 ventral segments.

CLAMBUS.

The type of Empelus is Litochrus brunnipennis Mann. from Sitkha. Having the anterior coxæ contiguous, transverse, conical, and prominent, it cannot be placed in the family Phalacridæ, to which Litochrus belongs, but seems to me to be a very obvious connecting link between Agathidium and Clambus. To Calyptomerus belongs Clambus oblongulus Mann., also from Russian America.

Sub-Family II.-BRATHINIDAE.

But one genus, Brathinus, is known of this sub-family, which is remarkably distinguished from the genuine Silphide by the prominent conical middle coxæ. The two species known to me are found about grass-roots in wet places, from Lake Superior to Nova Scotia, and are small shining insects, of graceful form, less than one-fifth of an inch long.

The head is oval, strongly constricted behind, with the front concave; eyes moderately prominent, oval, somewhat coarsely granulated; the gula behind the mentum is deeply channelled; the maxillary palpi are long and slender, the third joint is onehalf the length of the second, and the fourth is longer than the second; the labial palpi are moderately short, with the last joint a little longer. The antennæ are slender, almost filiform, with