47 



eating out the parenchyma at the circumference of the mine all 

 round, so that it forms a more or less roundish blotch ; and as it 

 almost entirely consumes the inner cells of the leaf, only the upper 

 and lower cuticles of the leaf remain, which causes the mine to have 

 a white and very conspicuous appearance. On August 23rd, 1908, 

 I found a leaf of Chenopodiiim albutn at Chiswick, containing two 

 mines, one of C. stipella and one of C. hermannella. The egg of 

 the latter had been laid on the upper surface and had hatched first, 

 the larva mining right across the space which was afterwards occupied 

 by the larva of C. stipella. 



The leaves of Chenopodium are frequently mined by Dipterous 

 maggots ; these make large, greenish blotches, and several larvae 

 occur in the same blotch. Though two or three larvae of C. herman- 

 nella often occur in the same leaf, they almost always keep to their 

 own mines ; yet I remember one case where two larvae, most 

 amicably, made a common mine for some distance. 



The ova are laid on either side of the leaf, but more commonly on 

 the under side, and usually close to the mid-rib or one of the lateral 

 veins. They are strongly attached. In shape the egg is ovoid, but 

 almost flat on the upper surface, rather truncated at the micropylar 

 end, and bluntly pointed at the opposite end. The long axis measures 

 o'34 mm. and the shorter 0-25 mm., while the depth is on an average 

 about o"i mm., but this varies considerably more than the other 

 dimensions. The sculpture consists of very deep longitudinal 

 wrinkles on the upper surface, the walls or sides are strongly pitted, 

 the pits being less deep at each extremity, and the micropylar rosette 

 is rather neat, with five oval cells. The colour is whitish, strongly 

 iridescent ; the green of the leaf shows through the egg, so that it 

 appears pale green when in situ. The eggs hatch within a week. 

 On hatching the larva partly fills the egg-shell with excrement. 



Larva., first instar. — Head rather large; width o"i2 mm. Thorax 

 rather swollen, body fairly cylindrical, tapering towards the bluntly 

 rounded posterior extremity. Segments not very well marked. Three 

 pairs of thoracic legs, strong and broad, with sharply-pointed claw. 

 Spiracles circular. I failed to see any trace of prolegs, tubercles, or 

 skin points. Head pale brown ; body very shining pale grey. A 

 dark grey transverse mark on the dorsum of prothorax ; dorsal vessel 

 green. Venter yellowish, with a broad orange band running from the 

 prothorax near the head down the centre of the body to the tenth 

 abdominal segment. As the larva is somewhat transparent the orange 

 band shows through, giving the larva a pinkish tinge on the dorsum. 

 Length, i mm. 



Second instar. — Width of head 0*24 mm. Head brown, body pale 

 yellow, ventral band not so broad in proportion as in first instar. 

 Four pairs of prolegs besides the claspers, but all without crotchets. 

 Length of larva i'5 mm. 



Third instar. — Width of head 0*4 mm. Head large, body fairly 

 cylindrical, rather transparent, narrowed slightly posteriorly. In 



