682 EXTERNAL ANATOMY OF INSECTS. 
half the Coleoptera belong to this section; in the Ortho- 
ptcra—the Blattina, Mantide, and Phasmide ; all the 
Lepidoptera except those butterflies called, tetrapi (Va- 
nessa, &c.); all the Trichoptera, Hymenoptera, and Di- 
ptera ;in the Neuroptera—Ascalaphus, Myrmeleon, He- 
merobius, Corydalis, &c.; and in the Aptera—Pulex *. 
Heteromerous insects are those in which the number 
of these joints varies in the different pairs of legs >. These 
variations, like the spurs, may be expressed by three 
figures, the first representing the anterior tarsus, the 
second the intermediate, and the third the posterior. I 
begin with 5: 5:4. This number represents those beetles 
that have been exclusively regarded as heteromerous by 
modern Entomologists—of this description is the Lin- 
nean Tenebrio, Meloe, &c., now subdivided into nume- 
rous genera; they have jive joints in the two anterior 
pair, and four in the posterior. The tarsal joints of the 
aquatic genus Hydroporus (a singular anomaly in the 
Order to which they belong) are expressed by 4:4: 5, 
thus reversing the number in the preceding tribe : other 
Heteromerous genera are to be found amongst the He- 
miptera. ‘Thus, in Ranatra the numbers are 2.1.1.5; in 
* The Cleride, which M. Latreille has placed in the pentamerous 
section, vary considerably in the number of their tarsal joints. Thus 
in general in Thanasimus the tarsi are pentamerous ; but in T’. for- 
micarius they appear to be heteromerous ; and in Enoplium, Opilo, 
Clerus and Necrobia they are tetramerous. M. Latreille’s expression, 
(N. Dict. d@’ Hist. Nat. vii. 172.) “le premier article etant fort court et 
caché sous le second,” seems to indicate that there is a jifth joint in 
some of these, the first being concealed under the second ; but I have 
never been able to discover it. Perhaps he reckoned the pwlvillus as 
a joint ? f 
> The term heteromerous properly belongs to a/l insects in which 
the different pairs of tarsi vary inter se in the number of their joints, 
and it is here used in that large sense. 
