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being often indistinct or wanting, especially in the posterior feet, and in 

 three families at least the Lathridiidte, Trichopterygidte and Pselaphid*, 

 two joints are wanting in all the feet, making them apparently but 

 three-jointed. 



The student will naturally inquire, why place these insects in the 

 pentamerous section ! The answer is, that they harmonize more closely 

 with the insects of this section in their other characters, whilst they do 

 not affiliate with the insects of the other sections which agree with them 

 in the number of tarsal joints. An examination of their other characters 

 will usually enable the student, after a little experience, to refer these 

 insects to their true position ; though cases sometimes occiu' which 

 puzzle the most astute entomologist. They can hardly be confounded 

 with the Heteromera, because these are, for the most part, much larger 

 insects, and the exceptionally small species belong mostly to the tribe 

 of Trachelides, which are distinguished from these and most other 

 beetles by having the head attached to the thorax by a narrow neck. 

 Tliey differ from the Tetramera in the form of the tarsi and also that 

 of the auteun;r. Almost all these small species with deficient tarsal 

 joints, have these parts slender and simple, whilst all the genuine Tet- 

 ramera ha^ e the tarsal joints somewhat widened and covered beneath 

 with a dense brush of short hair, and the last joint but one is wider 

 than the others, and divided into two lobes, between which the last 

 joint is inserted. The only jjentamerous beetles which have some of 

 their tarsal joints obsolete, and at the same time have the last joint but 

 one bilobed, are a part of the serricorn family of Cleridae. Some of the 

 short-winged scavengers with an irregular number of tarsal joints 

 (Staphylinidie), have a part of these joints widened but not bilobed in 

 the males, but here it is a sexual distinction, and is confined to the an- 

 terior feet. 



These small Pentamera, with variable tarsi, almost always have 

 strongly clavate antennse, except the Staphylinidse, and these are dis- 

 tinguished at once by their short wing-covers. The true Tetramera, on 

 the contrary, have the antennte filiform, or at most slightly and gradu- 

 ally enlarged toward the tip, except the snout-beetles (Curculionidce), 

 and these are readily known by their elongated rostrum. 



If, then, the student have in hand a small beetle whose place in the 

 system he cannot determine with certainty, from the number of tarsal 

 joints, let him first observe whether these joints are simple and of the 

 same width throughout, or whether the last joint but one is a little 

 wider than the others, and deeply notched or bilobed at the end ; and 

 next, let him examine the antennge, and observe whether they are slen- 

 der and filiform, or whether they are decidedly enlarged, at the end, 

 either gradually (clavate), or suddenly (capitate). 



