102 WATT 
Individual and geographical variation 
The study of dimensions and ratios described above shows (a) that measurable 
geographical variation occurs in even fairly closely related populations; (b) that 
considerable individual variation occurs within populations; (c) that all populations 
show sexual dimorphism (with females usually averaging larger than males); (d) 
that the degree of sexual dimorphism is geographically variable; (e)that one sex 
may be more variable individually than the other; (f) that the coefficient of 
variability varies geographically and (g) that the differences in variability between 
the sexes vary geographically. These generalisations are applicable to all 
geographically variable characters, with the qualification that most unmeasurable 
characters (e.g. punctation and sculpture) show an appreciable sexual dimorphism. 
Generic taxonomic characters 
The subfamily and tribal classification of Tenebrionidae is based almost 
exclusively on the external morphology of adults (Watt 1974; Doyen & Lawrence 
1979). From a practical point of view, as most adults in collections are dried, 
structures of the integument are most important. These are mouthparts, tentorium, 
meso- and metanota and hind wings, abdominal tergites, spiracles, endosternites, 
especially the metendosternite (cf. Crowson 1938, 1944), the male aedeagus and 
female genitalia and associated structures. 
As much morphological information as possible at the generic level is 
necessary for providing reliable data on which to base a sound supra-generic 
classification. This includes the morphology of larvae and pupae. 
Techniques 
Large beetles should be pinned wth strong stainless steel pins, not gummed by 
their ventral surfaces to pieces of card. Male genitalia are best extracted from the 
abdomen of relaxed specimens when they are being mounted. For dissection of 
female genitalia including delicate internal structures see Doyen & Lawrence 
(1979). Genitalia are removed from dried specimens by breaking off the abdomen 
and then soaking it in Barber’s beetle relaxing fluid or hot water (Beirne 1962) until 
the tissues are soft, or by soaking the whole insect in the fluid. On removal, the 
aedeagus is cleaned and mounted slightly on its side on a strip of card, which is then 
placed on the pin underneath the beetle; or in glycerine in a microvial. Female 
genitalia should be kept in glycerine, as they cannot be examined satisfactorily if 
dry. If the abdomen has been removed, it should be glued back on the specimen 
from which it came, 
For examination of internal structures it is necessary to treat the whole 
specimen with KOH solution. Treated specimens can be examined, drawn and kept 
in glycerine. It will probably be found desirable to make slide mounts in Canada 
balsam of small structures, such as mouthparts. 
It is very useful to have some specimens of each series properly fixed and 
preserved in 70% alcohol + 5% glycerine, together with larvae and pupae if these 
were collected at the same time. Properly preserved specimens are more useful 
than dried material. 
