The family character of this group which first attracts attention, is the large number of segments, each of which is composed of two unequal subsegments. The boundaries of the respective scuta of each pair of the latter are well marked by sutures, &c., but the sterna are completely consolidated. The head varies in form, size, &c., and furnishes the principal generic characters. The number of joints of the antennæ is fixed for the family, but nevertheless good specific, and even generic, characters, are derivable from these organs. The most important specific characters besides those before alluded to are founded upon, firstly, the peculiarities as to size, shape, proportion, &c., of the component portions of the head and its appendages; secondly, the color and form of the body, and the number of segments composing it; thirdly, the structure of the legs, especially of the last pair; and, finally, the markings and sutures of the scuta and sterna. I have never had an opportunity of examining very large suites of specimens, so as to determine positively the constancy of the various characters enumerated, but they probably do not vary a great deal.
Gen. 1. MECISTOCEPHALTUS, Newp.[1]
Segmentum cephalicum elongatum, angustum, latitudine plus duplo longius. Antennæ approximatæ, articulis obconicis. Subsegmentum prebasale sejunctuua sed basale subbasaleque coalita. Mandibulæ magnæ, intus denticulatæ. (Fig. 18.)
Cephalic segment elongate, narrow, more than twice as long as broad. Antennæ approximate; articles obconic. Prebasal subsegment separate, but the basal and subbasal coalescent. Mandibles large, within denticulate.
M. fulvus.
Fig. 18
M. fulvus, politus; capite dilute aurantiaco, punctato, pilis longis rigidis paucis; segmento cephalico antice truncato, postice illico angustato et vix truncato; antennis longis, pilis longis rigidis multis; labio profunde punctato, antice emarginato, medio sulco impresso; mandibulis distincte punctatis, pilis rigidis paucis, quadridentatis; segmento anali piloso; pedibus pilis longis, paribus 57.
Fulvous, polished; head light orange, punctate, with a few long rigid hairs; cephalic segment anteriorly truncate; posteriorly rapidly narrowed and scarcely truncate; antennæ with many long rigid hairs; labium profoundly punctate, anteriorly emarginate, impressed with a median sulcus; mandibles distinctly punctate, with a few rigid hairs, quadridentate; anal segment pilose; feet with long hairs, 57 pairs.
M. fulvus, Wood, Journ. A. N. S., new series, 1863, vol. v, p. 41.
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The cephalic segment is scarcely narrowed at all, except at the posterior end, where it is rapidly contracted, being indeed rounded off. The body is slender and polished. The
- ↑ Proc. Zool. Society, December, 1842, p. 179.
