132 Psyche [August 



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Kunckel. J. (1873.) Observations sur les Puces, en particulier sur les Larves des 

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Monthly Public Health Bulletins, Mass, 1909-1915. 



THE STIMULI WHICH CAUSE THE EGGS OF THE LEAF- 

 OVIPOSITING TACHINID^ TO HATCH. 



By Henry H. P. Severin, Harry C. Severin and William 



Hartung. 



Some difference of opinion exists as to the stimuli which cause 

 the eggs of the leaf -ovipositing Tachinidse to hatch. The eggs of 

 the leaf-ovipositing tachina contain fully developed larvae at the 

 time of deposition and are ready to hatch when swallowed by the 

 host. Townsend (4, p. 109) suggests "that the digestive juices 

 and conditions which the egg encounters in the alimentary canal 

 of the caterpillar act upon the chitin and cause the shell to weaken 

 so as to release the maggot." In direct opposition to this view, 

 Swezy (3, p. 29) writes as follows: "The shell of the egg is so 

 hard that it seems unlikely that it could be sufficiently affected 

 by the digestive juices of the caterpillar, quickly enough to allow the 

 maggot to escape from the egg, and also have time enough to pass 

 through the wall of the alimentary canal before it would be carried 

 along and be expelled with the frass of the caterpillar." Swezey 

 (2, p. 8) first ventured the opinion that the eggs "are so small as 

 to escape being injured by the jaws of the caterpillar in biting off 

 bits of leaf," but in a later paper (3, p. 30) he changed his view 



