Mining Micro- Lepidopterous Larva. 605 



the type of a new genus yet to be founded) into several groups 

 for the purpose of more ready comparison. 



In the first group I place the six genera, Nepticula, Cemiostoma, 

 Lyonetia, Phyllocnist'is, Bucculatrix, and LithocoUetis. Of these, 

 it will be observed that all, except Bucculatrix, not only remain 

 miners during the whole of their larval existence, but do not come 

 out of one mine to enter another: it is indeed true that the larva 

 of Phyllocnistis sal'igna will move from one willow leaf to another, 

 but this it does without ever coming out of its mine, for it pursues 

 its excavations down the footstalk of one leaf and then under the 

 bark of the twig to the footstalk of another leaf, so that it is com- 

 pletely under cover during its period of passage from one leaf to 

 another ; and in its curious habit it thus reminds us of the covered 

 way by which the Pope in times of trouble can retreat in safety 

 from the Vatican to the Castle of St. Angelo. 



Of the remaining five genera, two, Phyllocnistis and LithocoUetis, 

 pass the pupa state also within the mine. The former, when about 

 to change to the pupa, gives a slight curve to the edge of the leaf, 

 otherwise the leaf remains flat; but no LithocoUetis mine remains 

 flat, the leaf always curving, and sometimes very considerably, to- 

 wards the upper or underside, according as the larva happens'to 

 mine the upper or underside respectively. This curving of the 

 leaf is effected in the following way : the larva in the first instance 

 loosens the upper or lower epidermis to the extent that it will 

 ultimately require for its mine, and the loosened epidermis is then 

 gathered in folds together, and thus causes the remainder of the 

 leaf to curve towards that side. Hence mines of the genus Litho- 

 coUetis cannot be well shown from leaves which have been pressed 

 and dried, as their character is lost when they are flattened. Of 

 the three genera, Nepticula, Cemiostoma, and Lyonetia, of which 

 the larvae quit the leaf when full fed, the two first named form 

 cocoons, but the angulated pupa o? a Lyonetia is simply suspended 

 in a sort of hammock ; the cocoon of a Cemiostoma is of pearly- 

 white silk, pointed at each end ; that of a Nepticula is of yellow, 

 brown, red-brown, or violet silk, and of a roundish oval form. The 

 larvae o? Bucculatrix cease to mine when comparatively young, and 

 then feed on the external surface of the leaf, of which they gnaw 

 half the thickness. As was well observed by Professor Zeller, 

 they are the smallest known external-feeding Lepidopterous larvaa ; 

 their cocoons are exceedingly peculiar, of an elongate form, dis- 

 tinctly ribbed or fluted. 



To compare further the mines of these six genera, it may be ob- 



VOL. I. THIRD SERIES, PART VIII. DEC. 1863. T T 



