Mr Brindley , The 'procession of Cnethocampa pinivora. 103 
nest tree, it still remains to be shewn what advantages accrue 
from this formation when the larvae leave the tree to burrow. 
The very remarkable tendency to leave the tree and return to it 
without burrowing is perhaps the most obscure proceeding of 
this species. 
Oviposition by Tachinids. 
The Cap Ferret procession was the subject of continuous 
attack by Tachinid flies, apparently all of the same species. 
Unfortunately we did not secure a specimen, but with the kind 
assistance of Dr David Sharp and Dr F. J. H. Jenkinson we have 
since ascertained that it was almost certainly Dexodes macliairopsis , 
which Brauer and Bergenstamm* state is the Tachinid particularly 
infesting C. pinivora. The usual event was that a fly, after 
hovering over the procession, dropped suddenly on the sand and 
used its wings, slightly opened, as vertical props to support its 
body, whose ventral aspect faced the procession. With the tips 
of its wings thus resting in the sand, the fly employed most or 
all of its legs for pushing against the larvae as they passed, 
while it repeatedly extended its abdomen ventrally and forwards 
in an endeavour to inject its eggs. Apparently the usual attempt 
was to insert the ovipositor on the naked ventral surface of the 
larvae, while the pushing with the legs served to keep the fly’s 
head and thorax away from the lateral tufts of protective hairs. 
The unsteadiness of the fly in this curious position, the rapidity 
with which it made darts at the larvae, and the irregular 
stumbling of the latter under this hostile interference made 
exact observation difficult, but it seemed clear that in this 
sitting attitude a single fly often injected or endeavoured to 
inject several larvae in succession. It was, however, clear that 
there were very numerous failures to insert eggs in their intended 
host, as the ovipositor was as often as not thrust into the sand 
instead. Whenever the attack succeeded the larvae started vio- 
lently, the wound was evidently felt acutely. The length of the 
procession made it impossible to guess what proportion of the 
larvae received eggs, but bearing in mind how numerous were 
the Tachinids, the vigour of their attacks and the time the 
larvae were exposed thereto, the impression gained was decidedly 
that very few could have escaped the oviposition. In one case 
we noticed a different procedure by a Tachinid : it alighted on 
the head of a larva, ran rapidly, apparently with much discomfort, 
along its back, and then inserted its ovipositor close to the hind 
end. The longer hairs are grouped in tufts on either side of the 
mid-dorsal line and project outwards, so it seemed as though the 
Denk. Akad. Wien. lxi. 1905, p. 551. 
