238 



more during the following year. Thougli able to breed for one or two 

 seasons in the invaded territory, the locusts have seldom remained 

 long, moisture, in excess of that to which they were accustomed, 

 producing disease from which many die, the survivors migrating. 

 The lesser migratory locust {M. atlantis) also becomes more numerous 

 and destructive in dry seasons. The western wheat-stem sawfly 

 (Cephus sp.) is considerably reduced under natural conditions by a 

 dry season, but owing to the advance of agriculture and the cultivation 

 of cereals these sawflies have been enabled to continue their increase 

 by attacking wheat and rye, with the result that they are now a serious 

 pest. The Hessian fly {Mayetiola destructor) is also largely controlled 

 by lack of moisture. 



Snow is a very important factor in preserving insect life in winter. 

 This was shown by the effect of a lack of snow during the winter of 

 1914-15 in Manitoba on the Colorado potato beetle {Leptmotarsa 

 decemlineata), which had been a serious pest during the previous year. 

 In those parts, where there was only three inches of snow or less, the 

 beetles were found dead, crowded together in their winter quarters. 

 Where there was a depth of snow amounting to from four to six inches, 

 the survivors were considerably more numerous. At eight inches 

 about half the beetles survived, while a foot or more of snow apparently 

 provided complete protection from frost. 



AVeiss (H. B.) & DiCKERSON (E. L.). Plagiodera versicolora, Laich. 

 An imported Poplar and Willow Pest. — Canadiayi Entomologist, 

 London, Ont., xlix, no, 3, March 1917, pp. 104-109, 1 plate. 



Poplars as well as willows in New Jersey have been reported to be 

 infested by Plagiodera versicolora, a European species. The adult 

 beetles emerge in late April or early May after hibernation, and ovipo- 

 sition takes place after feeding. By early June, the adults have disap- 

 peared and the eggs have hatched. Three broods of beetles were 

 noted during the year, the last hibernating under the loose bark, etc., 

 and appearing as the first brood the following year. The eggs are 

 laid in circular or oval patches and almost invariably on the underside 

 of the leaves. 



This beetle is parasitised by the Chalcids, Coelopisthia rotundiventris, 

 Gir., and Pleurotrojns tarsalis, Ashm., the former being a primary 

 parasite and the latter probably a hyperparasite. It is also preyed 

 upon by a bug. 



Campbell (D.). Black Fly of Citrus. — Jl. Jamaica Agric. Soc., 

 Kingston, xvi, no. 2, February 1917, p. 50. 



The citrus trees belonging to the author with one exception were 

 infested with the citrus black fly (Aleurocanthus woglumi), and covered 

 with the sooty mould consequent upon the secretions from the larvae 

 of this pest. The exceptional tree was found to have a small nest of 

 ants on it, A. woglumi being entirely absent from it. The experiment 

 of putting an ants' nest on every tree was then tried with very satis- 

 factorv results. 



