NEPTICULA IGNOBILELLA. 279 



gradually increasing thickness, occupying half of the width of the 

 mine ; but the larva now ceases to mine in a slender gallery, but 

 forms a large irregular blotch, along the centre of which the excre- 

 ment is rather irregularly placed ; the larva thus mines from the edge 

 towards the mid-rib of the leaf, whereas the larva of N. pyymaeella is 

 at the same age proceeding in an exactly opposite direction, viz., 

 moving away from the midrib. These two larvaa have a considerable 

 resemblance, but the mines may be at once distinguished by the 

 colour of the excrement. When the larva is full-fed, it leaves the 

 mine by passing through the upper cuticle of the leaf (Stainton). 

 Wood writes: "The gallery is fairly long and slender, and rarely 

 occurs in the body of the leaf ; it wanders at first about the area 

 of a lobe before it reaches and follows the edge, and though this 

 wandering portion is afterwards absorbed by the blotch with which 

 the mine finishes, the fine frass-track remains undisturbed as evidence 

 of its former existence ; the frass of A 7 , ifjnobilella is black, both in 

 the gallery and blotch." 



COMPARISON OF THE MINE OF N. IGNOBILELLA WITH THAT OF N. 

 KEGIELLA. The blotch-miners, N. reyiella and N. ignobilella occur 

 together at about the same time, and are double-brooded, feeding in 

 the summer, and again late in the autumn. The small blotches that 

 they make at the tips of the lobes, with their yellow or yellowish 

 larvae, are certainly most provokingly similar, unless attention be paid 

 to one or more of the following points, when their discrimination 

 becomes as easy and pleasant as it before seemed impracticable. In 

 both the egg is laid on the underside, in N. reyiella quite on 

 the edge, in N. it/nobilella well away from it. As a consequence, 

 the whole course of the primary gallery of the former runs 

 along the edge, whereas the gallery of the latter wanders at first 

 about the area of the lobe before it reaches and follows the edge, 

 and though this wandering portion is afterwards absorbed by the 

 blotch, the fine frass-track remains undisturbed and is evidence 

 of its former existence. Next, N. reyiella deposits brown frass in its 

 gallery and black in the blotch, whereas the dejecta in N. ignobilella 

 are black in both gallery and blotch. Lastly, the head of the larva 

 of N. reyiella is pale brown, with the cephalic ganglia dark brown, 

 and consequently far more conspicuous than the head ; on the other 

 hand, the head of N, it/nobilella is blackish, overpowering the ganglia, 

 which are of a paler colour. I should add that a pair of brilliant 

 orange spots are frequently present on the front edge of the 2nd seg- 

 ment in A 7 , reyiella. I was inclined at one time to think that they 

 might be a sexual distinction, but careful breeding lent no support 

 to the idea. Thus, these species are distinguished by four distinct 

 characters, gathered from egg, mine, frass (colour) and larva. All 

 four are practically of much the same value, for all four are equally 

 constant and equally accessible to observation (Wood). 



LARVA. Length 2 lines ; pale greenish-yellow-grey, with the 

 dorsal vessel slightly darker ; the head is pale brown, the two posterior 

 lobes showing through the upper surface of the second segment 

 (Stainton). Wood, however, notes that "the larva is yellow or 

 yellowish in colour, its head is 'blackish,' and overpowers the ganglia, 

 which are of a paler colour." Stainton's description suggests the 

 larva of X. reyiella. 



