( lii ) 



Various suggestions were made in answer to Mr. Bacot's 

 main question by Mr. Green, Prof. Poulton, Rev. 

 G. Wheeler, Drs. Chapman, Cockayne and Eltringham, 

 and Mr. H. Willoughby Ellis gave reasons for ruling out 

 any possible electric agency in the matter. 



Egglaying of Trichiosoma tibialis, Steph. — Dr. T. A. 

 Chapman exhibited living specimens of the Sawfly Trichiosoma 

 tibialis, Steph., and eight eggs laid under the cuticle of haw- 

 thorn leaves, and read the following notes : — - 



I had this morning the pleasure of watching some speci- 

 mens of Trichiosoma tibialis, Steph. (our common hawthorn 

 species), laying their eggs. Broadly, their proceedings were 

 the same as I observed in the sallow species, as reported 

 in our Transactions, vol. 1914, p. 173. 



The process was very rapid, varying apparently according 

 to whether the leaf selected was very soft and succulent, or 

 slightly more mature. Though all the leaves available were 

 very young the oldest of them, whether accidentally or not, 

 were not selected. 



The greatest delay was, occasionally, in making an entry, 

 half a minute being taken in one instance, less than half a 

 minute for the complete direct penetration (as in fig. 4, PL. 

 XIII, 1914), and 15 to 20 seconds from that to the com- 

 pletion of the excavation (fig. 6, same plate) ; a rest then 

 occurred of about 8 to 10 seconds, then recurred the same 

 movements, as of cutting, with retreat of the terebra to the 

 position of PI. XV, fig. 10, and the simultaneous appearance 

 of the egg as if from nowhere. 



The progress of the supports was always steady and uni- 

 form, with no to-and-fro action, but the saws were constantly 

 moving rapidly to and fro, i. e. as one advanced the other 

 retreated. The extreme tips of the saws passed decidedly 

 further behind the supports than shown in my figures of the 

 sallow species, and consequently the strip of pocket cut 

 behind the supports (as seen in figs. 2, 3, 4, PL XIII) were 

 decidedly wider than in the sallow species. In the entry 

 (up to position fig. 4) the cutting was entirely done by the 

 ends of the saws, by which I mean their cutting margins, 

 beyond where the terebra begins to narrow. From position 



