42 HOUGHTON, ON THE MANGOLD-WURZEL FLY. 



root of the mangolds, here and there a larva ; indeed, if the 

 late broods do not remain as pujjoi under the ground, how 

 are they able to survive the winter, and by what means is 

 the continuation of the species to be carried on ? The larva, 

 at the time of the ruptui'e of the ovum, is about a line long ; 

 it is armed with two strong hook-shaped mandibles ; it grows 

 fast, arul reaches the size of about the third of an inch 

 in length, feeding upon the green parenchyma of the leaf. 

 For a description of the male fly, see ' The Journal of the 

 Royal Ag. Soc.^ for 1847, vol. vii, p. 411. The female fly 

 may be thus described^': colour of thorax light brown, 

 marked with five or six darker longitudinal lines, with four 

 or five series of black bristles similarly disposed ; abdomen 

 rather variable in colour, generally light brown or ashy 

 gray, rather glossy, with a distinct or indistinct darker line 

 down the middle, occasionally with irregular dusky patches, 

 which sometimes become so confluent as to give the abdo- 

 men a uniform dusky colour ; shape of abdomen oval, narrow 

 at the extremity ; head semi-orbicular ; eyes reddish-brown^ 

 remote, destitute of hairs ; antennae velvet-black, drooping, 

 arista bare ; face satiny white, with black bristles, having a 

 broad bright-chestnut band down the centre ; ocelli three, 

 situated on a satiny sub-triangular spot on the crown ; wings 

 the size of the body, tinged Avitli tawny at the base ; alulee of 

 moderate size ; legs black, tawny at the base, long ; proboscis 

 dark, wdth ta^vny tinge ; whole length nearly three lines. The 

 female is readily distinguished from the male; the more 

 general obvious difii'erences being — the shape of the abdomen, 

 which is oval in the female, but linear in the male ; the re- 

 moteness of the eyes, those of the male being nearly conti- 

 guous; and the less bristly character of the female. Tavo 

 important practical questions will naturally suggest them- 

 selves to the agriculturist; 1st. Is this insect likely to 

 abound again in such numbers as to afibct the mangold 

 Avurzel crops this year ? 2ndly. If it does so abound, what 

 remedial measures can the agriculturist adopt ? To both these 

 queries it is perhaps impossible to give a satisfactory answer. 

 It has been seen that the injmy done to the plants last 

 year is owing, in a great measure, to the large proportion of 

 female flies, a fact which depends on phenomena of the 

 nature of which we are wholly ignorant. A frost of some 

 weeks duration is generally considered to be the means of 

 destroying many noxious insects, and no doubt this is true 

 to some extent ; but it will be remembered that the winter 

 of 1860 was tolerably severe, and yet these Ant homy ice abounded 

 in the following spring. 



