— 210 — 



at its base. Just the same varieties occnr in the colouring of 

 the fly E. tenax. 



The fly appears in great abundance principally in autumn 

 and, when the days become chilly, in a semi-torpid state, 

 either sucking flowers, or crawling slowly upon walls and 

 fences. The american observer, just quoted, is probably right in 

 attributing to them a useful part in the fertilization of com- 

 posite flowers, and here we come across a most refreshing 

 instance of anglo-saxon enterprise, an attempt at once to 

 utilizo this fertilizing quality of the fly. The foUowing notice 

 speaks for itself. (« Insect-Life », Aprii 1893 which, by the 

 way, I received just as I was giving the fìnishing touches 

 to the present article) : Complaint being made about the 

 non-seeding of the Chrysanthemum in Jamaica, Mr. F. D. 

 A. Cockerell, Jamaica writes; « It seems that if ChrysantTie- 

 mum, which flourish well in our mountains, could be got to 

 seed, a profitable industry might be carried on, the seeds being 

 of high market -value. It at once occurred to me that our 

 want of Eristalis tenax might explain the non-seeding, and the 

 question has arisen shall we tiot import that fly? » etc. (1). 



The larva of E. tenax is the well-known rat-tailed larva 

 (ver à queue de rat, so called for the first time by Rèaumur, 

 1. e. IV, p. 443); it is figured in the same volume, piate XXX. 

 A long tail, with a telescopio arrangement for prolonging or 

 shortening it, enables the larvae to live several inches deep 

 in the water and to pump air from the surface. They fre- 

 quent putrid waters, sewers etc. and crawl out of them to 

 change into pupae in the vicinity. The vitality of these larvae 

 is said to be extraordinary, and for this reason Linné gave it 



(1) Jolin Hamilton. M. D. has an intoresting article : « On the probable polleni- 

 zation of Greenhouse Chrysanthemums by Eristalis tenax in: Entomologica Americana, 

 Brooklyn, N. Y. VI, p. 81, 1890. The author is inclined to ascribe to the Chrysanthe- 

 mitm-craze, which prevailed in the United States for some time, some influence in 

 the rapid propagation of this species in that country. It was always very abundant 

 in greenhousés. 



