EXTERNAL ANATOMY OF INSECTS. 519 
present, is regulated by no general rule with regard to 
the number of joints in the antennz of the insects that 
compose it. Several types of form in these organs distin- 
guish its discordant tribes. The fst is that of the Mphe- 
mere, in which the antennez consist of two short joints, 
crowned by a short, tapering, wnyjornted bristle. ‘The 
second is that of the Libellulina, similar to the above, 
but with a jointed bristle. The third is that of Psocus, 
in which the antenna has two short thick joints at the 
base, terminated by a long filiform bristle, consisting of 
seven or eight joints, and finer than a hair. Perhaps 
these three may be regarded as belonging to a common 
type. The fourth type is presented by the short fili- 
form antennee of Termes ; the fifth by the setaceous ones 
of Corydalis, Hemerobius, &c.; and the sixth and last by 
the clavate and capitate ones of Myrmeleon and Ascala- 
phus. Inthe Lepidoptera and Trichoptera orders the an- 
tennze, though varying in their general form in the three 
tribes of which Linné formed his genera Papilio, Sphina, 
and Phalena, with the exception of Hepiolus, in which 
the joints are few, are always multiarticulate:—we will 
therefore, without further delay, proceed to the Hymeno- 
ptera. In Latreille’s tribe Aculeata the general rule is, 
that the females shall have fwelve joints and the males 
thirteen. In his Ichneumonides the law seems to be, that 
the antennz shall be multiarticulate and setaceous ; but 
in most of the other tribes of the order, even those that 
in other respects are most nearly related,—as in his Ten- 
thredinete,—the number of joints of these organs varies 
without end. Thus in Hylotoma there are only three 
joints*; in Cimber lata’, five; in C. axillaris and 
* Jurine YLymenopt. t. vi. f. 3. » Lid 2. 
