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 Fompihis 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. Asilidm which have 

 no special form of insect prey, but attack indiscriminately, 

 are not as a rule mimetic. Such an exception as our own 

 Asilus crahroniformis 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 Asilid/e 

 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 {Bhizotrogns sauzi (?), Graells), among the swarms of 

 Orthoptera towards the summit of Penalara, on July 25, 

 1902. Mimicry, 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 (1. c, pp. 332, 333), specially select 

 ichneumons as their prey — in fact, 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 Asilida} 

 which specially attack single species of Aculeates, such, for 

 instance, as Dmnalina sp., described by Col. C. T. Bingham 

 as preying upon the model {Mdipona 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 

 Xylocopidm, 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 imfortunate that the 



