THE CANADIAN ENTOMOLOGIST. 97 



seed grain imported annually into the British Isles from countries known 

 to be infested by this tiy, together with the present rapid and easy methods 

 of transport, it is at least extremely probable that it has been introduced 

 over and over again, and it is difficult to understand why it has not long 

 before now secured a firm foothold there. May it not be hoped that the 

 law which applies with regard to many noxious weeds, will also be found 

 to hold good in the case of this injurious insect? The existence of any 

 plant as an aggressive weed in a given locality appears to be not so much 

 a question of the introduction of the seed, as of the plant finding there 

 the conditions suitable to its growth and healthy reproduction. There are 

 many plants, for instance, troublesome weeds here, which must have been 

 frequently introduced into Europe from this continent (or in some in- 

 stances taken back again to the place whence we originally received them), 

 but which have never yet taken forcible possession of cultivated ground, 

 e. g., the common Purslane ( Portulaca oleracea). Hound's Tongue or 

 Burrs (Cynoglossum officinale). Small Burrs ( Echinospermum Lappida)., 

 and the common Foxtail grasses (Setaria glauca and viridis); and then, 

 although relatively they are far fewer, there are some which must have 

 been frequently introduced on this continent, but which, except in a few 

 localities, cannot (or do not) exist for more than two or three seasons, 

 e.g., the common Scarlet Corn Poppy ( Pap aver Rhceas), Scarlet Pimpernel 

 ( Anagallis arvensis), common Groundsel ( Senecio vulgaris), Corn Grom- 

 well ( Lithospermum arvense), and the common Nettles ( Urtica dioica 

 and iirens). In the same way there is no doubt whatever that the Colorado 

 Potato Beetle ( Doryphora lO-lineata) has been many times conveyed to 

 the British Isles on transatlantic steamships, but not finding there condi- 

 tions suitable to its requirements, it has failed to establish itself. 



Miss Ormerod, quoting from Bulletin 4, U. S. Ent. Commission, tells 

 us that " the original habitat of the Hessian Fly is considered most pro- 

 bably to have been Southern Europe and Western Asia, i. e., about the 

 shores of the Mediterranean Sea," a district with a summer climate of far 

 greater heat and aridity than is found in the British Isles. Again, in 

 North America, where — whether introduced or indigenous matters not in 

 this connection — this pest to our sorrow flourishes to a most remarkable 

 degree, it has always dry, hot weather during the periods in which it passes 

 through its active stages. 



In view of the above facts, and notwithstanding that it has occurred in 

 considerable numbers in many parts of Great Britain during the past 



