1888.] 75 



this dates go for very little ; but I have little doubt Mr. Wood's spe- 

 cimens are early (for this season, not for an ordinary one) specimeus 

 of the summer brood. 



On August 3rd I find larva? of Gurtisellus on the ash saplings that 

 afforded hibernated larvae in May ; these are full-fed, or nearly so, 

 and are living in the bud for next year and the pith beneath it, and in 

 some instances between united leaves. Judging from the rapidity of 

 development of rustica last year, a very few days hot weather would 

 make them appear as moths. These larvae are associated with small 

 blotch mines in the ash leaves, but two that were found still tenanted 

 contained Dipterous larvae. 



Gurtisellus passes the winter almost invariably in the bark, ex- 

 ceptionally in the bud, but it equally goes to the buds in spring. But 

 I find it usually on suckers and the young ash grown for hop-poles, 

 and the buds open so rapidly that its usual habit is to find the buds 

 open so quickly that it has to bore into a young shoot, and then bore 

 downwards in the pith. On a rustica tree I found a larva doing so, 

 and settled that I had found a Gurtisellus among them ; he was large, 

 fat and pale, but he only produced rustica, but one of the largest I 

 have met with. 



A close comparison of many specimens of the larvae of Gurtisellus 

 and rustica led to no point of distinction being seized ; in some in- 

 stances the larvae were identical. The range of variation in colouring 

 is considerable : a dark larva has a broad chocolate band down the 

 back, marbled with greenish-yellow markings ; in others the sides only 

 of this band are chocolate, the centre being green ; arid in a few the 

 whole back is green. The chocolate is sometimes so pale as to be pale 

 reddish-brown. 



Gurtisellus is usually a larger, fatter and paler larva thau rustica, 

 which is usually dark and smaller. The pupa also varies from a pale 

 green pupa to one with a rich dark back, almost like that of the larvae ; 

 but whilst the mass of rustica are darker than the mass of Gurtisellus, 

 all varieties occur in either form. 



The summer brood of rustica is decidedly and uniformly smaller 

 than Gurtisellus, and its brown is so deep that black is perhaps a more 

 correct term. Spring rustica presents many examples of full size, and 

 it is possible that some of the smaller specimens are due to their 

 being bred, though small specimens are common enough among those 

 seen at large, not, however, a great number altogether. 



On rearing the spring brood of rustica the larger proportion pro- 

 duced rustica, but about one in six were of the Gurtisellus form. In 



G 2 



