250 THE entomologist's kecoed. 



"wrinkled, and will always serve to indicate the origin of any disturbance 

 caused by X. acetome in sorrel leaves, even if the discoloration of the 

 leaf be not more than 1mm. in diameter. 



Tlie larval habits. — "When leaving the egg the larva does not mine 

 directly to the upper-surface of the leaf, but works its way through the 

 parenchyma in a gradually ascending curve, completing perhaps two- 

 thirds of a circle before reaching the upper cuticle. After once reaching 

 the upper cuticle the larva continues mining just beneath it until full- 

 fed, when, like most other Nepticulids, it quits the mine to pupate. 

 Throughout the four stadia which it passes in the mine, it always 

 mines venter uppermost. When the larva in the first instar reaches the 

 upper surface of the leaf it continues the mine in ever-widening circles, 

 and, having made two circles or two-and-a-half, it lies up for its 

 first ecdysis. The mined patch at this stage measures l^mm. in 

 diameter, and is usually red, except where the two very irregular circles 

 of fine black excrement lie. The gallery of the mine itself is rather wide 

 in comparison with the larva, of a pale grey colour, with an irregular, 

 often interrupted, line of black excrement, which lies sometimes in the 

 centre of the gallery, and sometimes along one of the sides. The 

 length of the gallery mined during the first stadium is about 4mm. 

 The larva is exceedingly delicate, and it requires some care when 

 extracting it from the mine. It is pale ochreous, with a somewhat 

 swollen thorax, in which the small head is almost buried. It is quite 

 helpless when out of the mine. The duration of the first stadium in 

 some cases I noted as four-and-a-half days, but no doubt in warm 

 weather this time would be much shortened, as the larva I took from 

 the mine when seven days old was already in the third instar. As 

 with many of these minute larv*, the change of skin takes place 

 rapidly, especially in the earlier stages. One example in the first 

 instar had been feeding well certainly on the morning of September 

 17th, but, at midnight it was lying up for the change, and when I saAV 

 it again about 1 p.m. on the 18th, it was feeding vigorously, having in 

 the meantime cast oft' its skin. The larva in the second instar is bright 

 yellow, though when newly-changed it still shows the colour of the 

 first instar. It reaches to the length of l-2mm. Its mode of life 

 continues the same, and the mine does not alter in character, though 

 it is a little wider, and the black excremental track more distinct. I 

 have no notes as to the duration of either the second or the third 

 stadium, but if we find a mine about 2mm. in diameter, and especially 

 if it has one pale half-circle outside the red blotch, we may safely 

 conclude that the larva inside is in the third instar. When taken from 

 the mine it is almost as helpless as in the first instar, bright yellow in 

 colour, and about Ifmm. in length. It difiers chiefly from the s^econd 

 instar in size, and the body is more cylindrical, whilst the 9th and 10th 

 abdominal segments are longer and narrower in proportion, thus 

 approaching the appearance of these segments in the last instar. 



Its method of feeding is much the same, but it eats out the 

 parenchyma to a greater depth, especially shortly before lying up for 

 the last larval change. This is seen by the last half or three-quarters 

 of the circle in the blotch-like part of the mine being nearly as trans- 

 parent as the later serpentine portion of the mine. While still in the 

 first rather narrow pale circle the larva usually lies up for the third 

 moult. In the first three instars Nepticula acetosae exhibits a delicate, 



