NEPTICULA TRIMACULELLA. 349 



opposite spots being larger and broader, and placed directly above and 

 below each other (Frey). 



Egg-laying. — The egg is laid on the upperside of a poplar or 

 aspen leaf (Stainton). Nolcken, however, notes it as being laid on 

 either the upper- or underside, usually singly, but frequently several 

 on a leaf. 



Mine. — The larva makes a long, narrow gallery for some distance 

 close to one of the ribs ; it then diverges and makes a broader mine, 

 sometimes having the appearance of a blotch. The first third of the 

 mine is completely filled with dark grey excrement ; but as the mine 

 is made wider the excrement is placed irregularly along the middle 

 (Stainton). Frey notes it as " running in irregular curves, and with a 

 pale green colour in the broadened part." Nolcken adds that " the 

 frass in the first part of the mine appears to be deposited in a fluid 

 state, resembling much a very narrow, oft interrupted thread, the 

 frass becoming more solid and granular towards the end of the mine. 

 The frass-line is bounded by pale, but not conspicuous, margins, 

 which are of the same green colour as the leaf. The mine is only 

 very occasionally twisted sufficiently to assume a blotch-like form." 

 The mines are not always on the same side of the leaf, and Nolcken 

 notes that four eggs laid on the underside of one leaf produced one 

 " upperside " and three " underside " mines. 



Larva. — Length 2 lines ; very pale yellowish-green, with greener 

 dorsal vessel ; the head pale brown, the two posterior lobes showing 

 through the upper surface of the second segment ; the mouth and two 

 lines receding from it reddish-brown (Stainton). The larva mines 

 with the dorsum uppermost (Wood). 



Cocoon.— The cocoons (4) examined average 2-8 mm. in length, 

 and 2 mm. in width. They are somewhat irregular in shape, of an 

 oblong-oval outline, thinned off somewhat at the rim, and not much 

 domed above, the material tending to collapse irregularly after the 

 emergence of the imago. The cocoon varies from bright orange- 

 brown to red-brown in colour, and is somewhat plentifully covered 

 with loose, flossy, silken fibres, some of which is quite white in colour. 

 The empty pupa-case projects from what is the slightly broader end. 

 The dorsum is transparent and colourless, but the venter is of a some- 

 what dark greenish-grey tint. [Described July 13th, 1898, under a 

 two-thirds lens, from cocoons sent by Dr. Wood.] Stainton describes 

 the cocoon as " oval, rather flat, and brown in colour," Frey adds that 

 it is " smooth." 



Food-plants. — Populus tremula (Wing), P. pyramidalis and P. nigra 

 (Frey), P. canadensis (Heyden). 



Time of appearance. — The species is double-brooded, the imagines 

 appearing in May and August, from larvae feeding in October and 

 July respectively. Sang has obtained mines on June 23rd, 1874, 

 October 19th, 1863, Octobor 17th, 1873, at Darlington. Bower 

 notes mines as common on October 7th, 1891, at Lee, and October 

 21sfc, 1897, at Eltham, but Nolcken gives larvae as occurring on 

 August 18th, 1868, at Pyha, from which he bred imagines the follow- 

 ing spring. Threlfall bred imagines in April, 1878, from larvae 

 obtained at Leyland, October 14th, 1877. Stainton notes imagines 

 as bred on April 4th, 1855, May 3rd, 5th, 7th and 10th, 1864, June 

 16th, 1872, and August 3rd, 4fch and 26th, 1855, at Lewisham. 



