664 Mr. Edward Saunders on 
witnessed the oviposition of the banded variety mystacea 
in the nest of a ved-tailed carder-bee (Lombus derhamellus, 
Kirb.). The fly hovered round the nest for a few seconds, 
the bees paying no attention to it. It then alighted on the 
moss and quickly entered, remaining about eight minutes. 
At the close of this period it emerged, and at once flew 
away. Opening the moss below the point of its entrance 
and exit, about fifty or sixty eggs were found in a mass. 
These were exactly similar to the eggs sometimes laid by 
captured females of the species of Volucella. The fact 
that a banded fly should have laid in the nest of a red- 
tailed bee strongly opposes the interpretation of aggressive 
mimicry, originally offered by Kirby and Spence and 
followed by the present writer in former publications 
(e.g. “Colours of Animals,” London, 1890, p. 267). 
Another observation made on the same occasion also 
opposes the older interpretation. It is well known that 
the Aculeate models, when disturbed, commonly adopt a 
warning attitude in which the second leg is raised. On 
further irritation the whole body is generally tilted over 
on one side. In the sun Volucella is shy and readily takes 
flight; but on cold days and in the evening it becomes 
sluggish and semi-torpid. If disturbed in this condition 
I found that it raises its first leg in a manner clearly 
mimetic of the first warning position of its Bombus model. 
The anterior legs of flies perform such a variety of 
operations that selection would here have a comparatively 
easy task to produce a new movement of a simple kind. 
At the same time the general likeness of the attitudes is 
very striking, although different legs are made use of by 
model and mimic. 
The protective value of such a detail in the resemblance 
of fly to Bombus becomes sufficiently obvious, when it is 
remembered that the position is only assumed at a time 
of complete helplessness. On the other hand, it is most 
improbable that an attitude thus assumed could play a part 
in the aggressive mimicry of the one insect for the other. 
The facts now brought forward supply a solid foundation 
for the criticism of the older conclusions urged, in 1893, 
by Mr. W. Bateson, F.R.S. (“ Nature,” 1892, Vol. xlvi, 
p. 585, Vol. xlvii, p. 77). 
It is probable that the Volucellas, like the Asilids, are 
protected from insect-eating animals by their mimetic 
disguise, and that the resemblance of V. inanis to wasps 
