240 
Cr . J. Snowball. 
tion almost at right angles to the long axis of the body. Since most of the 
pupae in this condition are able to transform normally, it seems that the 
Nematodes are free living forms attracted to them by the moisture given off. 
Adult Cercyons, when kept in closed vessels with cow dung, often con- 
tain Nematodes in the posterior part of the alimentary canal and genital tract 
as well as on the moist body surfaces. There is no reason to believe that the 
presence inside the body is due to anything more than the tendency to migrate 
into any aperture. 
C. ANNELIDA. 
Fresh cow dung attracts earthworms which will consume large quantities 
if it is applied to garden beds containing them. They are also of frequent 
occurrence in heaps of fourth stage cow dung which has retained moisture. 
Nothing definite is known of the degree of competition they offer to the true 
dung insects. 
9. FEATURES OF THE SUCCESSION IN COW DUNG. 
Having referred to various aspects of tlie biology of the insects concerned, 
it is now^ possible to draw up a scheme showing the features of the succession, 
defined according to the stage through which the cow dung passes, as set out 
in section 4. 
First Stage. 
This is characterised by the activities of dung insects on the surface of the 
fresh dung. The Sepsids, Borborids, Calliphorids, Otitids, and Muscids 
appear to feed on the liquid dung in such a haphazard manner that the order 
varies for practically every dung. 
The dung bettles are also prompt in arrival and again no particular order 
can be defined. The Staphylinids, Hydrophilids, Histerids (in season) and 
Aphodiines, except A. ambigims, all commence to penetrate either through 
natural crevices on both surfaces or by creating apertures in the superficial 
skin. 
Toward the end of the first stage, the number of flies diminishes. The 
Calliphorids leave first, the only attraction for them being the soft dung now 
covered with a firm skin, and then the large dung-breeding Muscids after ovi- 
position. The Sepsids and Borborids remain longer, and the former may be 
seen ovipositing over some days. The predatory Dolichopodids and Creo- 
philus erythrocephalus also leave when the numbers of their prey diminishes. 
Second Stage. 
The surface layers of the cake become penetrated by the dung beetles. 
Sepsids and Borborids are still present. Mites and Collemi^ola appear early 
in this or late in the first stage. Although the eggs of Muscids and Sepsids have 
hatched, the small size of the larvae renders them inconspicuous. Adult 
Psychodids are to be found o\'ipositing on cakes in the shade. 
Third Stage. 
The dung is extensively penetrated by beetles. In many cases an un- 
jienetrated core near the low^er surface is left but many cakes are completely 
riddled. The activities of Cercyons and Aphodius lividus, by admitting air 
into the dung, give it its characteristic black colour. The latter part of this 
period is primarily one of immature stages. The poi^ulation of Sepsid, Droso- 
philid, and Psychodid larvae becomes very high. Cercyon and even occasional 
Scarab larvae aj^pear tow^ards its end, as the emigration of adult beetles begins. 
