98 [October, 



eastwards at once, because the necessary conditions for its existence 

 were wanting on the immense plains it had to cross, just as the 

 Colorado beetle lived in the Rocky Mountains on Solanum rostrafum, 

 and did not spread eastwards until civilization brought the potato 

 plant (Solanum tuberosum), and thus bridged over for that beetle the 

 distance between its native mountains and the Atlantic coast. The 

 condition which civilization brought and which favoured the rapid 

 eastward progress of ^. tenax consisted in the drains, sewers, and 

 cesspools, those necessary concomitants of crowded centres, and the 

 usual abodes of the larvae of EristaJis. 



If we accept this train of reasoning, and I do not see any escape 

 from it, we must carry it further, and admit that E. tenax is a com- 

 panion of civilization, and becomes common with its diffusion only. 

 In early times, when there were no drains and cesspools, E. tenax 

 must have been much less comuion. AVe have a parallel case in the 

 gradual diffusion of Teiclwmyza fusca, which became common in cities 

 with the introduction of certain modern improvements in cleanliness ; 

 (compare its history in the paper by Dr. Laboulbene, Ann. Soc. Ent. 

 Yr., 1867, p. 33). 



At this point another, apparently very distinct subject, forces 

 itself upon our attention. It is well known that the ancients believed 

 that carcasses of dead animals (especially oxen) produced hees. Virgil, 

 in the Georgics (iv, 285) speaks about it ; even modern authors like 

 Aldrovandi (De Anim. Insectis, p. 58, edit. 1602) and Moufet (Theatr. 

 Insect., p. 12, 1634) relate the most wonderful stories: "Aiunt ex 

 horum cerebro gigni reges et duces, ex carnibus vero apum vulgus. 

 Nascuntur item reges ex medulla spiuse, tamen ex cerebro nati pul- 

 chritudine, magnitudine, prudentia et robore aliis antecellunt, etc." 

 (Moufet, I. c.*). Lion's carcasses are also spoken of, and the passage 

 in the Book of Judges xiv, 8, refers to a similar case : " And he 

 (Samson) turned aside to see the carcass of the lion ; and behold, 

 there was a swarm of bees in the body of the lion, and honey," etc., 

 the honey, of course, being a stretch of imagination. 



Now, in all these cases, what were mistaken for bees must have 

 been species of Eristalis. Even nowadays E. tenax is frequently 

 taken for a bee by non-entomologists. Such occurrences are less 

 familiar to us than to our forefathers, because carcasses are not left 

 lying about now as they were before. But a case in point has been 

 observed by Zetterstedt in Lapland (Dipt. Scand., ii, p. 666). He saw 

 Eristalis antliojihorinus swarming round the carcass of a sheep : " Ad 

 cadaver ovis putridissimum, aquse stagnanti maximam partem immersum 



* Chap, iii, " De creutione, generatione, et propagatione Apum." 



