]7S [August, 



would expect to find protected by mimetic resemblances. In every 

 way they may be said to present all the requirements of an ordinary 

 case of mimicry. 



The Echinomyia, however, does not present so ordinary a case. 

 It is a wonderfully strong and robust species, belonging to a group of 

 parasitic species, all of which are strong and robust, and ordinarily 

 neither need nor possess any such protection as a mimetic resemblance. 

 It is well protected on the body by strong hairs, answering, to some 

 extent, the purpose of spines, and is very strong on the wing ; it is 

 very large, too, many specimens being 8 or 9 lines long. It, however, 

 occurs at this time (March) when other insects are scarce, and it must 

 be conspicuous and so tempt its foes, and although common on this 

 particular occasion at Wyre Forest, I do not think it is usually a 

 common species, at least, I never saw it before ; altogether, although 

 it does not answer the usual requirements of a mimetic species, yet 

 there are obviously good reasons why a resemblance to the strong and 

 and usually unmolested Bomhi would be an advantage to it. We 

 accordingly find that it does possess some such resemblance, though 

 imperfect, and it is just this imperfection which is its most interesting 

 feature, and is to some extent the reason for these notes. 



Many or all of the opponents of the theory of mimicry urge very 

 strongly the diflicult question — how does the resemblance arise?, in 

 early stages it can be of no use to its possessor. But here, I think, 

 we have a case showing how mimicry may arise, and even the early 

 stages be of use. The TachinidcB do not, as a rule, resemble in the 

 least degree any Hymenoptera, they are quite unlike bees. The 

 Echinomyice are a genus of unusually large and well-developed TacJii- 

 nids, some of which (fera and ferox, for example) are simply ordinary 

 Tachinids in appearance, though unusually large, and quite unlike 

 bees ; they are summer species : ursina, however, a spring species, 

 though closely allied to these others by a comparatively slight 

 alteration in colour, a development rather than an alteration, and the 

 increase of its hairs in number and size, at once and unexpectedly 

 somewhat resembles Bomhus muscorum, and almost certainly must 

 derive some protection from even this superficial resemblance, at a 

 time when food is being so eagerly sought by insect foes. It only 

 needs a still further increase in hairiness, and to fold its wings over 

 its body, and it would be an almost perfect mimic ; and supposing its 

 nearest allies to be lost, we should wonder how the early stages arose. 



147, Hall Eoad, Handsworth, 



Birmingham : May, 1894. 



