THE SO-CALLED BUGONIA OF THE ANCIENTS. 499 



become so common tliat " hiindieds were caught." A few years later 

 the specifes was reported trom nearly all the States of the Union, includ- 

 ing- California and Washington Territory; also from Canada (Montreal, 

 common, as stat(Hl by Mr. Caultield in Cariad. Entom., 1884, p. 138). 



A communication made by the American dipterologist. Dr. Williston, 

 proves that the invasion has gone, not from the Atlantic border to the 

 West, as one might have expected, but, on the contrary, from West to 

 East. Dr. Williston had seen a specimen of E. lenax hidden among a 

 lot of duplicates in Prof. Riley's collection, bearing a label St. Louis, 

 Angust, 1870. Upon drawing Prof. Riley's attention to the Hy (which 

 the latter did not previously know by name) he was assured that the 

 species had long been familiar to Mr. Riley in outhouses about St. Louis. 

 The surprising rapidity however with which the species spread along 

 the Atlantic coast soon after its first appearance renders it probable 

 that it can not have existed in St. Louis very long before 1870, other- 

 wise it would have reached the Atlantic sooner. We are thus driven 

 to accept the following outline of its history. We know that it exists 

 in Japan and eastern Siberia; from there it must have migrated to the 

 North American Pacific coast perhaps long ago. It did not spread 

 eastward at once, because the necessary conditions for its existence 

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

 rado beetle lived in the Rocky Mountains on ISolanum rostratum, and did 

 not spread eastwards until civilization brought the potato plant {Sola- 

 nnm tuberosum) with it, and thus bridged over for that beetle the dis- 

 tance between its native mountains and the Atlantic coast. The con 

 dition which civilization brought, and which favored the rapid east- 

 ward progress of U. tenax, consisted in the drains, sewers, and cess- 

 pools, those necessary concomitants of crowded centers and the usual 

 abodes of the larva of Eristalis.* 



The immigration of E. tenax into New Zealand is of a still more 

 recent date than that in North America. The Catalogues of the New 

 Zealand Diptera, by Nowicky (1875) and Prof J. W. Button (1881) do 

 not mention it. It was first noticed in Wellington (North Island) in 

 October and November, 1888. In June, 1890, Mr. W. W. Smith (Ash- 

 burton, South Island) writes: "It is now widely dispersed and very 

 ])lentiful in thp South Island." (Notes on Uristalis tenax in New Zea- 

 laud, by W. W. Smith, in the Entom. M. Mag., London, 1890, pp, 240- 

 242.) 



About Australia, with regard to E. tenax, I am sorry to say, I have 

 no information whatever. 



'' All the details aud references about the jjeographical diatribntiou of Eristalis 

 tenax will be found in my two articles: 



1. Facts concerning the importation or non-importation of diptera into distant 

 countries (Trans. Ent. Soc, London, 18^4, pp. 489-496). 



2. Some new facts concerning Eristales tenax {Entom, Monthly May., London, 1886, 

 jtxiii, pp. 97-99), 



