NOTES ON THE LIFE-HISTORY OF NEPTICULA ACETOS.E, STT. 103 



Notes on the Life- History of Nepticula acetosae, Stt. {tilth plate), 



(Concluded from vol. xx., p. 252). 

 By ALFEED SIGH, F.E.S. 



If the lai'va of Xepticula acetosae finds a suitable situation for 

 the cocoon, it commences spinning a very short time after leaving 

 the mine, but more often it wanders some distance before settling 

 down to spin the cocoon. At first the larva spins a net-work 

 of a rather open nature, which probably defines the boundaries 

 of the structure. This is then filled up from within, and after 

 some hours a much closer net-work is visible. This is again filled 

 up, so that after some hours (twelve in one case, I noted) 

 the larva has completely hidden itself in the white cocoon. The 

 cocoon, entirely of silk, is rather flat, generally almost pointed at one 

 end, and rounded at the opposite end. It appears to be formed of two 

 valves, joined together at the pointed end and up the sides, but less 

 firmly joined at the broader end. Through a slit in the broad end the 

 pupa thiusts itself on emergence. At the bottom of the pointed end, 

 the old skin of the larva may be found. This, from its now contracted 

 state, gives the settB, which do not contract, an exaggerated appear- 

 ance, so that the skin appears to have belonged to a quite hairy larva. 

 In the summer-time the transformation of this species is rapid. Some 

 larv«, which were still in their mines on August loth, 1908, produced 

 imagines on August 28th. In warm weather there appears to be a 

 succession of broods. I took larvje still in their mines on October 10th, 

 but did not search after that date. This species hybernates in the 

 pupal stage. I have not yet seen the imago in the held, but those I 

 had in captivity were fond of hiding out of sight, and very quick in 

 their movements. 



There are yet one or two points concerning the larval mines to be 

 mentioned. The mine takes the form of a fairly circular patch 

 containing about seven concentric turns of black excremental lines. 

 The mines are usually dexti-ally coiled, but may also not rarely be found 

 sinistrally du-ected. The last three-quarters of the last whorl of the 

 circular part of the mine, is wider and paler, and develops suddenly 

 into the serpentine portion, which is variable in length, and terminates 

 just beyond the semicircular slit by which the larva quits the mine. 

 If the two cuticles of the leaf be separated where a mine has been 

 formed, it will be noticed that in the cu'calar blotch-part of the mine, 

 the excrement is nearly all deposited on the upper cuticle, whereas in 

 the serpentine or gallery-part of the mine, the excrement is all on the 

 lower cuticle. The first arrangement is that adopted by the larva 

 when in any of the first three stadia, and the second, that made use of 

 in the fourth stadium. The parenchyma of the sorrel-leaf is usually 

 stained a deep red for some space round the mine, but not all red 

 blotches in sorrel-leaves are due to Septlcula acetosae. Some appear to 

 be caused by a leaf-fungus, and others by the natural process of decay. 

 The leaves, especially of the sheep-sorrel, in autumn, are often entirely 

 red, and where the plants grow thickly, add colour to the landscape. 



Larva. — Fiist iiistar: Head very small, almost enveloped in the 

 large prothorax. Meso- and metathorax both large, but less than the 

 prothorax. The abdominal segments are smaller than the metathorax, 



