34 



IDENTITY OF THE INSECT. 



In regard to the specific identity of this insect, there seems 

 little room for doubt that it is the Aleyrodes vaporariorum of West- 

 wood. Although Westwood's description (i) may not be sufficient 

 for identification, Signoret's description (2) is quite complete, and 

 the correctness of the latter's determination has never been chal- 

 lenged by later European writers. On the contrary, J. W. Douglas 

 (7), who was later the best authority on this group of insects in En- 

 rope, speaks of Signoret's work in such a manner as to leave no 

 doubt that the species described by Westwood and re-described by 

 Signoret were the same. 



Signoret's drawings and description of the pupa differ from 

 those of the present writer only in minor details. His determination 

 of the limits of the second and third abdominal segments differs 

 slightly from mine ; consequently, according to his drawing and de- 

 scription of the pupa a pair of wax rods arises from the second ab- 

 dominal segment, whereas I found the corresponding rods on the 

 third abdominal segment. His drawing of the ventral side of the 

 first instar is obviously inaccurate in many respects, but it probably 

 resembles the first instar of Aleyrodes vaporariorum quite as much 

 as of any other species. 



ORIGIN AND DISTRIBUTION. 



This insect was first described in 1856 by Westwood (1), who 

 supposed it to have been imported into England from Mexico. 

 Signoret, in 1868 (2), intimated that the species might have been in- 

 troduced into Europe from Brazil. Whatever its origin may have 

 been, it is at present widely distributed in greenhouses in Europe 

 and in the Northeastern United States, and has also recently been 

 reported from Canada (27). 



FOOD PLANTS. 



The list of food plants of the Greenhouse Aleyrodes is so ex- 

 tensive that it would seem almost advisable to list only those plants 

 which the adults reject and upon which the immature stages cannot 

 subsist. Westwood (1) in his description of the species says in re- 

 gard to its food plants : " It especially attacks the leaves of Mexi- 



