1889.] A New Cattle-Pest. 587 
observed, and as I can corroborate. Rather interestingly, too, 
like other domestic animals, it seems subject to modifications of 
climate and environment to such an extent that several varieties 
have been described from the different countries it inhabits. 
Almost equally widely distributed are the other plagues of the 
housewife,— the blue-bottles, Calliphora vomitoria, C. erythroce- 
phala, Uicilia ccesar, and L. coniicina, — all of which have dis- 
tributed themselves from Europe throughout the length and 
breadth of North America, and some even into South America.' 
In fact, little as we know about the Muscinae of our country, 
nearly a score of species are known to be identical with European 
But we have no right to say that all such species are impor- 
tations; some, perhaps many, of them undoubtedly are, but assur- 
edly not all of them are. And even those whose original habi- 
tats have been extended through commerce, we may as rightly 
believe to have been exported, in many instances, as imported. 
Commerce with America far antedates the systematic or even 
superficial study of insects, and the dissemination of insects 
would as likely be to as from Europe. The Colorado beetle 
is a striking instance coming within our own observation. The 
Hessian fly is another that stands almost on the border line 
of history, and though, as Professor Riley shows, we have every 
reason to believe that it was originally an European insect, yet 
had reliable evidences of its occurrence in North America ex- 
tended back a few years earlier we should never have known 
whether we had Europe to thank for the pest, or Europe us, as 
she has more recently for the phylloxera and grape-vine fungus, 
or whether, indeed, there should be no exchange of thanks at all, 
the insects being "at home" in both continents. The screw- 
worm fly, Lucillia macellaria, occurs from Canada to Patagonia ; 
will it become naturalized in Europe ? 
The distribution of many species in both Europe and North 
America opens up a number of interesting questions about which 
» Calliphora vomitoria has been accredited to South America, but in the examina- 
tion of considerable material from Brazil I have not found either of the Lucilis, though 
