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V. The Egg-laying of Trichiosoma (Tenthredinidae). Bv 

 T. A. Chapman, M.D., F.Z.S. 



[Read February 4th, 1914.] 



Plates X-XVI. 



In the Presidential Address to the Entomological Society 

 on January 12, 1912, by the Rev. F. D. Morice, we have a 

 resume and critical estimate of all that was known up to 

 that date concerning the action of the ovipositors (saw, 

 terebrae) of the sawflies {Chalastogastra), together with 

 some very careful and important observations by Mr. 

 Morice himself on one species of the group. 



This Address stimulated my interest in the operation 

 of oviposition in the sawflies, which I had often wished to 

 observe, but had never succeeded in actually seeing. 



It curiously happened that in the spring of 1913 an 

 extremely favourable opportunity of doing so occurred to 

 me, and the details observed seem to be worth relating, 

 because they were so very clearly seen, and for another 

 circumstance which appeared as a result, viz. that they 

 differ to some extent in the different species (or genera ?) of 

 sawflies, and that consequently my observations are not 

 merely a confirmation of Mr. Morice's report, but rather an 

 extension in a new direction. 



It was on the 22nd April, 1913, that I saw in the marshes 

 at Reazzino, near Locarno, a specimen of Trichiosoma 

 betuleti (?) in the act of laying an egg in a leaf of a small 

 smooth round-leaved sallow. I watched it lay a second 

 egg, but not having a lens did not see much of the process. 

 On the way home I found another specimen of the same 

 species at rest on a poplar trunk. A good many searches 

 on later occasions failed to result in the discovery of any 

 further specimens. These two flies I took home and kept 

 in captivity for two or three weeks. 



I was very much struck by their quiet sluggish behaviour 

 and by the fact that during the whole time I had them, 

 neither of them made any attempt to use her wings. 



I think it is probable that both had already laid the 

 majority of their eggs, as they were rather hollow in appear- 

 ance and only laid a dozen or so eggs each for my benefit, 



TRANS. ENT. SOC. LOND. 1914.— PART I. (juNE) 



