the canadian entomologist 367 



The Susceptibility of the Eggs of Aphis Pomi and Aphis 

 AvEN.E TO Hydrocyanic Acid Gas Formation. 



BY WILLIAM A. ROSS, DOMINION ENTOMOLOGICAL LABORATORY, 



VINELAND station, ONTARIO. 



It is of economic interest to note that the fumigation of young 

 apple trees with hydrocyanic acid gas just before or shortly after 

 the buds commence to swell not only controls the San Jose scale, 

 but it also destroys the eggs of aphides. 



In the spring of 1914, we procured from a local nursery seven 

 apple trees well stocked with the eggs of Aphis pomi and Aphis 

 avencE. Three of the trees were fumigated for forty-five minutes with 

 hydrocyanic acid gas (1 oz. KCN to 100 cubic feet, 1:1:3 formula), 

 and the others were used as checks. None of the eggs on the fumi- 

 gated nursery stock hatched, whereas large numbers hatched on 

 the check trees. 



This spring the foregoing experiment was duplicated, and 

 the same highly satisfactory results were obtained — 100 per. 

 cent of the aphid eggs were destroyed. 



In the 1914 experiment the nursery stock was fumigated 

 eight days, and in the 1916 experiment six days before the eggs 

 on the check trees commenced to hatch. 



A CHANGE OF SYNONYMY IN XYLOMIGES (LEPID.). 



BY F. H. WOLLEY DOD. 



The species described by Smith as Xylomiges pallidior is 

 identical with simplex Walk. Harvey's crucialis, hitherto mis- 

 identified as simplex, is distinct. Even after seeing Smith's tj^pe 

 and possessing specimens of both forms, it was some years before 

 I was at all sure that the species really existed, as the difference 

 appeared to be merely varietal. But, as time went on and I 

 saw and acquired more material, their distinctness became ap- 

 parent. Ha\'ing become satisfied as to the existence of two species, 

 judged by superficial characters alone, I got Mr. Tams to make 

 several mounts of the genitalia of each, including Vancouver 

 Island specimens of both forms. These were found to differ in such 

 a way as to make their separation quite easy. Being at present 

 separated from my specimens and mounts by several thousand 

 miles, I am unable to state concisely just what these differences 

 are, but hope to make it clear some day. 



November, 1916. 



