662 Mr. Edward Saunders on 
it a specially advantageous model, the likeness under such 
favourable conditions assisting it in the struggle with 
enemies against which the sting of Pompilus would be a 
defence. The striking and conspicuous colouring of this 
Aculeate renders it especially suitable as a model. 
Furthermore, the detailed resemblance may have been 
built up on a foundation provided by a slightly greater 
initial resemblance to this rather than any other Aculeate 
genus. 
This appears to be the most feasible explanation 
of Asilid mimicy as a whole. <Asilide which have 
no special form of insect prey, but attack imdiscriminately, 
are not as arule mimetic. Such an exception as our own 
Asilus crabroniformis recalls in a general way the type of 
Aculeate colouring and pattern which is commonest and 
most conspicuous in its region, and is probably therefore 
independent of the advantages due to special association. 
Neither do we find mimicry prevalent among the Asilidx 
which exhibit decided preferences, but not in the direction 
of specially-defended prey, such, for instance, as Dysmachus 
trigonus, which clearly selected a much less abundant 
beetle (Lhizotroqus sauzi (2), Graells), among the swarms of 
Orthoptera towards the summit of Pefalara, on July 25, 
1902. Muimicry, on the other hand, is common among 
these predaceous Diptera when they attack the Hymeno- 
ptera in any special degree. We can probably distin- 
guish two classes of mimetic resemblances among such 
Asilid flies. In the first we may place Dasypogon diadema 
and the slender ichneumon-like Dioctrias which, as Colonel 
Yerbury has observed uC c., pp. 332, 333), specially select 
ichneumons act, all examples in which 
the attacks are upon a group rather than upon a particular 
species. The second class, in which mimicry is even more 
common and more exact in its details, comprises the Asilide 
which specially attack single species of Aculeates, such, for 
instance, as Damalina sp., described by Col. C. 'T. Bingham 
as preying upon the model (Melipona apicalis), which it re- 
sembles with extraordinary precision (1. c., p. 334). Further 
examples are probably to be found in ‘the Hyperechias, 
which bear so wonderfully perfect a resemblance to the 
Xylocopidx, and, as is believed, prey upon these Aculeates. 
Indeed, Mr. E. E. Green has only recently observed one 
circling round its Xylocopid model in Ceylon (Proc. Ent. 
Soc. Lond., 1904, June 1). It is unfortunate that the 
