1920. J 



225 



a dozen eggs tliat seemed mature, but the ovarian tubules each con- 

 tained a series of 4 to (5 or more of dwindling sizes, so that bej'ond the 

 smallest there might be others still smaller, but not visible in my rough 

 procedure. It apj)eared that to mature these and keep the fly alive 

 some nutriment would be necessary. A fly, still alive, was offered honey 

 and water, which it accepted at once and continued drinking it for some 



<^~v) 



Rough camera sketches to illustrate eggs laid on leaf of Salix sp. by Ptemnidea 

 {Nematiis) pai-ida (figs. 1-5) and Nematus ribesii (fig. 6) : a, natural surface of 

 leaf ; b, portion of leaf denuded of cuticular film over surface to which egg is 

 attached ; c, scrap of cuticular film shown on removing egg. 



Fig. 1 : P. pnvida ; egg rolled off surface of attachment to leaf, with bit of cuticular 

 film rolled off egg, but still attached to it and to leaf. Fig. 2 : end view of egg : 

 the irregularity of outline has no relation to attachment to leaf, though the sur- 

 face of attachment is perhaps slightly flattened. Fig. 3 : diagrammatic, to 

 show how the cuticular film is thro-vvn back by the egg being laid between it and 

 the leaf ; it adheres to the egg, but not so firmly as the egg to the leaf. 

 Fig. 4 : egg removed from leaf, with scraps of cuticle adhering to it. Fig. 5 : to 

 show white cuticular film left when egg is rolled off successfully in the right 

 direction ; it stands out conspicuously white against the dark green of denuded 

 and un denuded leaf. Fig. 6 : egg of N. ribesii showing the peculiar outline 

 with one end raised prow-like ; d is intended to show, as near as can be judged » 

 the depth to which a portion of the egg-shell is trapped and forms a short flange 

 in tlie leaf incision. Enlargement of all figures about X27. 



minutes. It had another drink of hone}' and water on August 3rd, but 

 this morning, August 5th, it is dead. It had laid 6 eggs (within th-e- 

 last fiiur days), but its remains show the abdomen very hollow and 

 transparent. Xo J d have emerged. 



My attempts to remove an egg from the leaf ended in breaking up 

 the egg, until I found that judicious lateral pressure was occasionall}'' 



