NOTES ON THE LIFE-HISTORY OF NEPTICULA ACETOS.E, STT. 249 



which species of dock. It is, however, clear that he meant one of the 

 larger species. 



The ovHtn. — The comparatively very large egg is laid almost always 

 on the underside of the leaf and usually away from the midrib and 

 from the margin. Several eggs may be laid on the same leaf, but 

 always separately. The largest number I have seen is twenty, on a 

 leaf of tl. acetosa. There were twelve on one side of the midrib and 

 eight on the other, all laid on the underside. On another leaf there 

 were nine eggs, seven of which were laid on the upperside, which is 

 however, quite the exception. Before being laid, I imagine, the egg 

 is ovoid. The shell is evidently very soft, as after the egg is laid it is 

 found to be very wide and Hat, as though it had been poured on to the 

 leaf in a molten state. It takes the exact impression of that portion 

 of the leaf on which it lies. This causes its outline to become veiy 

 irregular and often much indented, and also greatly adds to the diffi- 

 culty of detecting the micropyle, a feat I have not yet accomplished. 

 If one could persuade the moth to lay on glass, the micropyle could, 

 no doubt, be made out. In outline, the egg is ovoid, or even sub- 

 triangular rather than circular. There is a long axis which measures 

 0-38mm., and a shorter measuring 0-27mm. Of course the ova vary 

 a little in size, but the smallest measured 0-32mm. by 0-23mm. They 

 are very flat but vary in height, and I think 0-06mm. would about give 

 the average height. There is no visible sculpture on the surftice of the 

 shell. When newly-laid the ova are colourless and transparent, but 

 as the larva advances in growth its yellow colour shoAvs through the 

 shell, generally first appearing as a yellow line, running partly round 

 the boundaries of the egg. A certain time before hatching, the larva 

 can be seen lying in a curved position within the egg. The head is 

 partly buried under the last portion of the abdomen, and there is an 

 orange-coloured streak in the centre of the alimentary canal. Just 

 before hatching the orange streak becomes concentrated, and, while the 

 larva is eating its way into the leaf, it travels up to the anus and is 

 eventually expelled. When the larva of PJn/llocnistis safusella eats its 

 way out of the egg-shell into the leaf, its action is very vigorous, and 

 within tw^o hours it will be hidden in the leaf, yepticida acetosae is a 

 great contrast with this, as its movements, when eating its way through 

 the base of the egg-shell into the leaf, are exceedingly gentle. It has, 

 however, much harder Avork to do than the other, which simply severs 

 the cuticle of the leaf from the upper cells of the parenchyma, while 

 the Nepticulid tunnels into the parenchyma and consumes the more 

 solid portion, as well as the juice. One larva, which I noted more 

 particularly, began to penetrate the leaf at 4.20 p.m. By 6.20 p.m. it had 

 worked about half its head into the leaf. At 10 p.m. it had nearly 

 withdrawn the thorax from the egg-shell. When I again saw it, the 

 next morning, it had already left the egg-shell, and at 1 p.m. it was 

 lying just under the upper cuticle of the leaf. At the least, the larva 

 requires twelve hours to get clear of the egg-shell. On examining the 

 forsaken shell we see that, where the larval head lay, there is a semi-cir- 

 cular hole in the cuticle of the leaf and a line of excrement, this running 

 round the shell where the body of the larva lay, and ending in a little 

 patch of orange. The egg-shell remains for weeks attached to the 

 leaf, and may be noted as a silvery-grey flat speck in the centre of the 

 circular part of even quite old mines. Under a lens it appears much 



