Proceedings, 1920. 97 



rethinned onions was estimated to average 24 tons per acre ; the balance of 

 the field was a total loss. 



From the observations made on the experiment the following conclu- 

 sions were drawn : The fresh bait was attractive to the fly. Where the 

 plates had been allowed to dry no flies were attracted to the poisoned 

 molasses remaining. Instead of weekly renewal of the bait as suggested by 

 the Wisconsin experiments, it was found that daily renewal was necessary 

 under our dry conditions. Instead of daily renewal of the bait, water was 

 added to the plates to replace evaporated moisture ; this possibly was not 

 done until after the bait was so dry that the water would not mix readily 

 with the poisoned molasses; consequently the flies were able to obtain 

 moisture from the bait without absorbing the poison. In the middle of June 

 infestation was found to be very heavy, and the second thinning appears to 

 be mainly responsible for the excellent crop obtained, the cost of which was 

 certainly warranted, but careful work is necessary to make the thinning a 

 success. 



In the spring of 1919 experiments will be conducted to find, if possible, 

 a more attractive bait ; also methods of application more suitable to our dry 

 conditions in relation to the life-history will be tested. 



References. 



(1) Gibson & Treherne, Ent. Branch, Ottawa, Bui. 12. 



(2) Severin & Severin, Jour. Econ. Ent., \'ol. 8. 1915, p. 342. 



(3) Donald J. Caffrey, Ent. Rept., Connecticut, 1911, p. 287. 

 (4j N. F. Howard, Journ. Econ. Ent., Vol. II., 1918, p. 82. 



SOME NOTES ON THE TENT-CATERPILLAR. 



Bv A. B. B.^iRD, Assistant Entomologist, Entomological Branch, 

 Ottawa. 



During the past summer the tent-caterpillars have been attracting the 

 attention of every orie in and around the Cities of Vancouver and Victoria, 

 and judging from the supply of egg-masses to be seen at the present time 

 this pest inay be expected in even greater numbers in 1919 unless control- 

 work is undertaken in a thorough and systematic manner. These cater- 

 pillars must not be confused with another destructive species, the fall 

 web-worm (Hyphantria sp.), which were also very abundant in Vancouver 

 and the Lower Eraser \'alley last year, but which appear much later in the 

 season, usually about the end of July, after the tent-caterpillars have 

 disappeared. 



Two distinct species of this insect occur in British Columbia — the 

 common or orchard tent-caterpillar (Malacosoma pluvialis) and the forest 

 tent-caterpillar (M. disstria var. erosa). Their life-histories, habits, and 

 control are quite similar, however, and they will be treated together in this 



