SECTION OP PENTAME1IA. 
35 
4. If the tarsi are dilated and bilobed and the antenna clavate, tlie spe- 
cies belongs to the tribe of snout-beetles (Curculionidce), in the tetrame- 
rous section, or the family of Erotylidae, or that of Coccinellidae, in the 
triinerous section. 
5. Beetles with distinctly serrate antenna belong almost exclusively to 
the families of Serricornes proper, iu the pehtamerous section ; but this 
rule also has a few exceptions. The pea and bean weevils (Bruchida), 
iu the tetramerous section, usually have the antennae decidedly serrate; 
and a few small families of the division of Trachelides, in the hetero- 
merous section (Rhipiphorida and Pyrochroida), usually have the an- 
tenna; serrate in the females, and flabellate or branched in the males. 
C. All beetles with lamellate antenna belong to the division of Lamel- 
licornes proper, iu the pentamerons section. Only in very rare in- 
stances the branches of a pectinate or tlabellate antennae are somewhat 
flattened so as to resemble the true lamellate. An example of this is 
found in the little beetles of the genus Phlceotribus in the family of 
Scolytidae. 
Section 1. PEXTAMERA. 
Usually five joints in all the tarsi , one or two of them being sometimes' deficient in very small species; all 
the joints usually slender and simple, except that the anterior, or anterior and middle tarsi arc some- 
times dilated and brush-like beneath, as a sexual distinction of the males. 
It is seen by this formula that the pentamerous section is distin- 
guished not only by the number, but also by the form and structure of 
the tarsal joints, the tarsi in this, and also in the succeeding or hetero- 
merous section being, with but few exceptions, slender aud simple, and 
clothed only with scattered hairs or bristles, whilst iu the third and 
fourth sections the tarsi are widened and covered beneath with a dense 
brush of short hairs, or hair-like papillae, and the penultimate, or last 
joint but one, is almost always bilobed. It is important to bear this 
two-fold distinction in mind, inasmuch as the form and structure of the 
tarsi often give the clue to the classification of small species in which 
the number of the joints is deficient or difficult to be determined. This 
has been already more fully explained in the general remarks on pages 
30 to 34. 
The ambiguity arising from the dilation of some of the tarsal joints 
in the males of certain species, can always be avoided by directing the 
examination to the hindermost tarsi, which are never so dilated. 
This is the most numerous section, and comprises, as a general rule, 
the largest and most highly organized species iu this order of insects, 
though it also contains many small species. 
They can be divided into six sub-sections, founded upon their habits 
and the nature of their food, and distinguished primarily by the struc- 
