18 
MEMBBACIDJE. 
The Membracidae are not characterised by the noxious odours common to many 
bugs. The orifices to their supposed stink glands have been confused with the true 
stomata, with which they have no connection. The demon-like forms of some Centrotidae 
might be thought to be sufficiently deterrent, without the adjunct of a vile odour. 
The Genitalia .—It has been pointed out that what are called secondary characters 
(that is, those less important to an animal’s econoni}^) are those the least likely to 
undergo change when the animal is persistently forced into new conditions of life. 
r l hey keep their functions, but they may be modified in form. What may be called 
the plastic organs are those obviously the most liable to be affected, and thus it happens 
that they do not readily lend themselves to generic classifications. 
So it is that wing-neuration often breaks down where most it is wanted, and 
sexual characters which might seem well suited for separating genera, fail us from 
their wonderful adaptability to altered conditions. An insect may be winged or 
apterous without losing otherwise its general distinctions; or this character may affect 
only one sex. 
This is true also of the external sexual organs of insects. Modifications are 
produced which do not impair the primary functions. Ovipositors, stings, and 
piercing saws in the females may be answered by elaborate claspers, styles, and long 
intromittent appendages in the males. 
The diversity of form and the aptitude for variation appear in these organs to be 
an embarrassment rather than an assistance in classification. Authors have more or 
less successfully described and figured the sex-organs, but up to the present time 
much is left to be done, before genera can be founded, or based on the singular forms 
assumed b}* these parts in species. 
The external genitalia of the Membracidae do not however greatly differ in form 
from the allied Jassidae and Cercopidae, but perhaps they are less complex. 
The female parts are represented by six pieces— viz., two valves, two inner rasps 
or sheaths, and two sword-like blades, but slightly serrated, and without any marked 
ovipositor. We may infer from what is known of Tenthredo that there is some 
alternating action in these saws, and that grooves are cut in bark or rind into which 
the female inserts her eggs. The field naturalist here might help us in showing this 
part of the life economy of these insects.* 
The males in many species have the lower parts of the ninth abdominal segment 
produced into a pointed process, whilst the upper part develops two lobes, which fall 
one on each side, as in most other males of Homoptera. 
* An interesting account of the habits and the oviposition of Ceresa bubalus, by C. L. Marfatt, may 
be found in Nn. 1, vol. vii. of “ Insect Life,” Washington, 1894. The subject will be discussed when 
that .species is described later on in this monograph. 
