A Consideration op the Insect Population Associated 
WITH Cow Dung at Crawley^ W.A. 
225 
42 species with this habit. Sphaeridium, a coprophagous genus wliich I iiave 
not seen recorded from Australia, is associated with Cercyon in both England 
and Prance, especially in cow dung (Lacordaire, 1854), and in Ceylon and 
Japan aquatic species of both occur (Sharp, 1884, 1890). 
Cercyon haemorrhoidalis. Fab. 
This introduced species is represented at both Crawley and Katanning 
by two easily separated varieties. One is most numerous between November 
and June (PI. 1, Fig. 1), the other between Juno and November, both being 
present all the year round. The species occurs also in carrion, decaying 
grass, and horse manure. 
With the Aphodiines, Staphylinids, and Histerids, they arrive at the 
dung soon after dropping, tlie odour being apparently the attracting stimulus. 
At first they congregate on the under surface or in the natural cracks of the 
dung. From these vantage points the work of penetration begins. The 
adults are coprophagous, and tunnelled out dung is eaten, since no waste is 
found outside infested cakes. The area of penetration is peripheral at first, 
then the insects concentrate on the upper surface. Many dungs are found 
with an almost unaltered' core, though the superficial layers are completely 
penetrated underneath the firm outer crust which is pierced by numerous 
holes. 
Under favourable conditions of fine days anti high temperatures cakes 
may be riddled into a bran-like mass in a single day. Whore heavy rain has 
fallen or low temperatures prevail, the process of penetration may bo greatly 
slowed down, and may not even occur to any extent at all. 
The specimens of Cercyon haonorrhoidalis run into dark places only when 
a dung is disturbed, and are otherwis(> tolerant of light. 
The beetles leave the dung after a varying period, which is generally 
from four to fourteen days. It may be mucli longer and fluctuates con- 
siderably from cake to cake under identical external conditions. During 
this period, which is one of tro])liic activity, eggs are deposited, since larvae 
begin to appear in the third stage dung. I have not been able to isolate tlie 
eggs of the species in spite of the larvat> being fairly plentiful. Numbers of 
females caged with dung in tlie laboratory died without oviposition, yet 
dissection showed their ovaiies contained numerous oocytes. 
Exactly what the legless mandibulate larva (PI. l,Fig. 2) feeds on is a 
problem. The gut contains a translucent reddish-brown lk|uid full of oil 
globules which cannot certainly be recognised as a derivative of cow dung. 
Development occupies approximately 10 to 14 days in pure cow dung. 
Pupation generally occurs in the dung itself in a small cavity excavated 
by the propupa near to the outer surface. Wluu'o the dung lias remained 
very moist, pupation may occur in the sand below the dung. No cocoon of 
any sort is formed. The jiuj^ae are of the usual exarate coleopterous type 
and, like many other white or yi'llow immature stages of insects, is negatively 
phototropic. 
The pupal period was observi'd to range from three days in April (18° C.) 
to II days in .September (18-9° C'.). The life cycle from egg to adult took 
less than 29 days at temperatures from 13*9° C. to 10-1° C. in September 
anti October, 1941. 
