168 



The Naturalist. 



The Tachiniidoe, as the family is called, are very difficult to name 

 and describe, individuals of the same species varying greatly in size 

 and even structure, and distinct species being very closely related to 

 each other ; so it is only by the examination and comparison of 

 numerous specimens that it is possible to acquire a critical knowledge 

 of them. There are many points of great interest respecting their 

 natural history, one of the greatest being whether the same species 

 of fly generally or always selects the same species of larva, or whether 

 different species attack the larva of the same insect. Systematic 

 authors give but little information upon this subject, though a few 

 desultory facts have been recorded ; thus it is quite unknown upon 

 what caterpillar the larva of our largest species {Echinomyia grossa) 

 feeds. In this (dipterology) as in other branches of entomology, the 

 determination and arrangement of species possess much more attrac- 

 tion than the higher and more philosophical part of the science, viz., 

 the study of the habits and manners of insects. We really know very 

 little more now respecting the economy of the parasitic diptera than 

 what was recorded long ago by those giants in entomology — De Geer 

 and Eeaumur. 



Being interested in the study of Tachiniidoe, I am induced to make 

 these few remarks in the hope that some of the numerous lepidop- 

 terists who are readers of this journal may be led to assist me by 

 carefully preserving all diptera (I do not want hymenopterous para- 

 sites, though they are equally interesting) which may issue from the 

 cocoons of butterflies or moths in their breeding cages, taking note of 

 the species from the cocoon of which they are bred. I will gladly 

 undertake to name (as far as I can) any of the flies sent to me, and in 

 this way some definite knowledge of their economy may be in time 

 obtained. 



About two years ago, Mr. Mosley, of Huddersfield, kindly sent me 

 two or three specimens of Exorista vulgaris, which he had bred from 

 Thecla quercus, and last year Mr. B. Cooke, of Southport (late of 

 Bowden), gave me one of Nemorea maculosa, which issued from the 

 cocoon of Botys verticalis. I have received a great many species from 

 other entomologists, but, with the above exceptions, without any 

 notice of the insect upon which they were parasitic. 



To give some idea of the extent of this family, I may mention in 

 conclusion that Meigen describes 315 European species in his great 

 work on diptera, and F. "Walker, 166 British ones in the second vol. 

 of the " Insecta Britannica," and says he only includes half of them. 



Bradford, Feb. 25th, 1879. 



