256 ENTOMOLOGICAL SOCIETY 



bud-scales. After several attempts, the ovipositor is forced 

 in and glides down under the bud-scales to the base of the 

 bud-axis, which it penetrates from without inwards. This 

 can only be accomplished by imparting to the ovipositor a 

 direction at an obtuse or right angle to the course it followed when 

 entering. The natural curvature of the ovipositor here stands 

 the fly in good stead, but it requires a vast expenditure of time 

 and strength before it can penetrate the heart of the bud." 



Referring to Biorhiza apt era (which is the agamic form of 

 Teras terminates) , he says that the female seeks by preference 

 the greater terminal buds and seeks to bore into them. " The 

 pricking is done in a very different way from that of other gall 

 flies. After a suitable bud has been found, the fly stops, turns 

 its head downwards, and directs its abdomen to the point of the 

 bud. In this position it inserts its ovipositor somewhat below 

 the middle of the bud, in or upon the tissue from which terminal 

 growth proceeds. After the fly has pushed in its ovipositor it 

 withdraws it, and goes oh boring one canal after another in the 

 stratum which the egg is to occupy, until the whole layer is rid 

 dled like a sieve. When the operation is finished, the eggs are 

 successively pushed into the pricked canals, where they lie so 

 thickly together that they look like a continuous mass. The 

 amount of work which the fly goes through in laying its eggs in 

 this way is astonishing. After having been occupied for hours 

 in boring these numerous canals, it appeared to me inexplicable 

 that it had as yet laid no eggs; I found, however, that it bores 

 all the canals for their reception before actually laying a single 

 egg. This part of the work requires much time, as to which I 

 have made the following observations. 



" On January 27, 1878, a fly was put upon a little oak, and 

 soon began to prick a bud ; when it had finished the first bud, it 

 went on without interruption to another, and was altogether 

 eighty-seven hours busily employed laying its eggs. In these 

 two buds I counted 582 eggs." 



The process of oviposition in the Cynipidre is a very elaborate 

 one and has been much written about. Adler gives a most full 

 and elaborate description of the mechanism of the ovipositor, and 

 particularly of the ventral plates and bundles of muscles by which 

 the terebra is worked. The structure of the ovipositor is well 

 known, and its parts homologize with those of the same organ in 

 all Hymenoptera. It consists of a large bristle or seta and of 

 two spiculae which mortise into it and form the channel down 

 which the egg passes. The seta occupies half the area of a trans 

 verse section of the terebra, and the two spiculas occupy the other 

 half. The seta has two tenons, and a central canal which con 

 tains an air vessel, a nerve branch, and some sanguineous fluid. 



