664 Mr. Edward Saunders on 



witnessed the oviposition of the handed variety mystacea 

 in the nest of a red-tailed carder-bee {Bomhus derhamcllns, 

 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 eiglit 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 VohiceUa. 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 Bomhus 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 Bomhus 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 



