34 THE ORDER OF OOLEOPTERA, 



have a part of these joints widened but not bilobed in the mak\s, but 

 here it is a sexual distinction, and is confined to the anterior feet. 



These small Pentamera, with variable tarsi, almost always have 

 strongly clavate antenna?, except the Staphylinidir, and these are dis- 

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

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

 ally enlarged toward the tip, except the snout-beetles {Curctilumidcv), 

 and these are readily known by their elongated rostrum. 



If, then, the student have in baud 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 slender and sim- 

 ple or dihited and brush-like beneath, with the last joint but one deeply 

 notched or bilobed ; and then let him examine the antennsie, and observe 

 whether they are slender and filiform, or whether they are decidedly 

 enlarged at the end, either gradnally {clavate), or abruptly {capitate). 



1. If the tarsi are simple and the antemuv filiform, the species maj^ 

 belong to some one of a number of diverse families {Garahidw, Elater- 

 id(e, Mordellida', Melandryidw, Cistelida', and a few smaller families) ; 

 but the beetles with this combination of characters are rarely of very 

 small size, and they are, therefore, the more easily determined by their 

 other characters. 



2. If the tarsi are simple and the antennce clavate or capitate, the in- 

 sect may be referred, with very few exceptions, to some one of the fami- 

 lies of scavenger beetles in the pentamerous section. This rule embra- 

 ces a large proportion of very small- sized beetles, and will, therefore, 

 be found of great use to the student in narrowing the field of his 

 inquiry. A few apparent exceptions exist in the heteromerous families 

 of Diaperidixj and Tenebriouida^, but the former can be usually distin- 

 guished by their perfoliate autenni^', and the antennie of the Tenebrio- 

 nidic are usually so slightly enlarged toward the tip as scarcely to be 

 entitled to the name of clavate. Other partial exceptions are found in 

 the family of Scolytidaj, or short horned wood-borers, all of which have 

 strongly clavate antennae, and some of which have simple tarsi ; but 

 many of them have the last joint but one slightly bilobed. 



3. If the tarsi are dilated and bilobed. and the antennce filiform, the in- 

 sect belongs to the family of long-horned borers {Cerambycida'), or to 

 that of the plant-beetles proper {Chrysomelidw, etc.) The tarsi thus 

 formed are almost always spongy on the under side. Only a few par- 

 tial exceptions to this rule are found, and these are in the heteromerous 

 families of G5demerid*, Anthicidje, and a few others ; but in these the 

 tarsi are usually but slightly dilated, and but little, or not at all, spongy 

 beneath. 



