THE NEPTICULIDES. 177 



some excretory substance present in the frass, I am quite unable to 

 say. At any rate the whole virtue of the operation seems to be 

 exercised whilst the larva is still young, and, once accomplished, the 

 life or death of the creature is of little or no consequence." He 

 considers that in the very earliest stage the larva " catches and im- 

 pregnates the sap in its passage out of the vascular bundles." He 

 points out that even if the larva of N. mbbimacidella, N. apicella, or 

 N. intimella die in their mines in an early stage, the part of the leaf 

 in which they commenced to form their mines is still preserved, and 

 he says: "the only plausible explanation I can see is that some 

 substance is produced which, being absorbed by the vascular bundles 

 among which the larva is burrowing, gets distributed to the parts 

 of the leaf they supply, where it is taken up and appropriated by the 

 cells." 



The phenomenon is noticeable also in the mines of the Lithocolletids. 

 In those of the Nepticulids the patch fades insensibly into the 

 surrounding area, in the Lithocolletids it occupies exactly the area 

 of the mine itself. The virtue of the preservation, Wood says, "lies 

 in the first stage of the work, viz., in the separation of the cuticle, for the 

 larva, having effected this, may come to grief, and yet the patch it has 

 so cunningly marked out for its future use will remain green and fresh, 

 as if nothing were amiss, whilst the rest of the leaf may have long 

 since gone through the whole series of autumnal changes." He states 

 that although the Nepticulid larva does not eat down the veinlets to 

 the same level as the parenchyma, it does nibble them, and thus gains 

 access to the vascular bundles, and so to the general current of the 

 circulation. In this way, by the assumption of some product of the 

 larva as the real efficient cause, and mechanical irritation but a 

 subsidiary one, Wood allies the process with that of gall formation, 

 especially as seen in the Cynipidae, in which the poison is provided by 

 the larva and not by the parent insect at the time of oviposition. 



The Nepticulid pupa has the ' ' eye-collar ' ' exceedingly well-developed. 

 By examination of the pupae of this superfamily, Chapman was able to 

 prove that this (eye-collar) was the case of the maxillary palpus, and 

 that its appearance of coming not from the mouth, but from under the 

 antennas, and, passing inwards, is in agreement with the actual fact. 

 The palpus 5 (or 6 ?) jointed, on leaving the maxilla passes backwards 

 in the angle between the head and the prothorax, until it is situated 

 deeply beneath the antenna, then it turns forwards to the antenna, 

 and only reaches the surface by emerging from beneath the antenna, 

 and, turning inwards, forms the " eye-collar," which contains only 

 its terminal joints, the others being concealed deeply. The parts of 

 the Nepticulid pupa separate readily on slight violence, so much so 

 that it is not easy to be sure whether the first free segment is the 

 second abdominal or the third, but Chapman believes it to be the latter. 



When the imago is matured, and ready for emergence, the pupa 

 forces its anterior segments out of the cocoon. It is remarkable that 

 the newly-emerged imagines do not, as do most newly-emerged 

 Lepidoptera, stand so that the expanding wings may hang downwards, 

 but remain on a horizontal surface, the wings gradually stretching 

 until the full size is attained, when they are thrown perpendicularly 

 over the back. 



As the chief imaginal features, Heinemann discusses (1) the colour 



L 



