HETEROPTERA. 
667 
The characters used in separating families relate to the antennae and 
hemelytra. The terms used are shown in figures 435 and 436 ; the stu¬ 
dent wishing to identify species will find the terms used in the Fauna 
of India fully explained in Volume I of Rhynchota ; we have used this 
as the basis of classification throughout the group. 
CORIUM- " 
Fig. 436— Wings of heteroptera. 
Heteroptera. 
Front of head not touching the coxae. The tegmina usually lie flat 
on the abdomen and the basal half is thickened. 
The sub-order falls into distinct series, the first, Gymnocerata , having 
conspicuous antennae, the second, Cryptocerata, having the antennae more 
or less concealed; the former includes all the terrestrial Heteroptera, and 
those that live on the surface of water ; the latter includes all the Hete¬ 
roptera that live in water as well as one species living on mud ( Pelogonus) 
and a few on land (Mononyx). The sub-orders are thus easily recognised 
in the field. A key to the families will be found in the Fauna of India, 
Rhynchota, Volume I. 
A feature of the great majority of the Heteroptera is the aromatic 
odour they protect themselves with. This odour is due to the secretion 
by special glands of an oily fluid, which is excreted at will from the 
odoriferous orifices and rapidly volatilises. The odours are very marked 
in Pentatomidce, Coreidce, Lygceidce, Pyrrhocoridce, some Reduviidce, and 
in Cimicidce: they are ordinarily characteristic of the plant-feeding groups, 
only a few of the predaceous Reduviidce having them. Throughout 
the Heteroptera, the imago is a very important and active stage of life, 
the previous development being practically only a growth in size, with 
the gradual development of wings. There is none of the specialisation of 
