XXIII GALL-FLIES 529 



the egg really passes along the canal of the borer. Hartig 

 thought that it did so, and Kiley supports this view to a limited 

 extent. Adler, however, is of a different opinion, and considers 

 that the egg travels in larger part outside the terebra. It should 

 be remembered that the ovipositor is really composed of several 

 appendages that are developed from the outside of the body; 

 thus the external orifice of the body is morphologically at the 

 base of the borer, the several parts of which are in longitudinal 

 apposition. Hence there is nothing that would render the view 

 of the egg leaving the ovipositor at the base improbable, and 

 Adler supposes that it actually does so, the thin end being 

 retained between the divisions of the terebra. Eiley is of opinion 

 that the act of oviposition in these Insects follows no uniform 

 system. He has observed that in the case of Callirhytis clavula, 

 ovipositing in the buds of Quercus alha, the eggs are inserted by 

 the egg-stalk into the substance of the leaf, and that the egg- 

 fluids are at first gathered in the posterior end, which is not 

 inserted. " The fluids are then gradually absorbed from this 

 exposed portion into the inserted portion of the egg, and by the 

 time the young leaves have' formed the exposed [parts of the] 

 shells are empty, the thread-like stalk has disappeared, and the 

 egg-contents are all contained within the leaf tissue." He has 

 also observed that in Biorhiza nigra the pedicel, or stalk, only is 

 inserted in the embryonic leaf-tissue, and that the enlarged portion 

 or egg-body is at first external. The same naturalist also records 

 that in the case of a small inquiline species, Ceroptres politus, the 

 pedicel of the egg is very short, and in this case the egg is thrust 

 down into the puncture made by the borer, so that the egg is 

 entirely covered. 



Some Cynipidae bore a large number of the channels for their 

 eggs before depositing any of the latter, and it would appear that 

 it is the rule that the boring of the channel is an act separate 

 from that of actual oviposition. Adler distinguishes three stages : 

 (1) boring of the canal ; (2) the passage of the egg from the base 

 of the ovipositor, where the egg-stalk is pinched between the two 

 spiculae and the egg is pushed along the ovipositor ; (3) after the 

 point of the ovipositor is withdrawn, the egg-body enters the 

 pierced canal, and is pushed forward by the ovipositor until it 

 reaches the bottom.^ 



^ Adler and Straton, Alternating Generations, 1894, p. 119. 

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