HOUGHTON, ON THE MANGOLD-WURZEL FLY. 41 



uuinbci* of small, -wliite, cylindrical ova, in clusters varying 

 from two to six or eight together. On holding these up to 

 the light I could clearly see from the track, Avhich extended 

 from the ruptured ova between the cuticles to the larvae in 

 another part of the leaf, that these were the undoubted ova 

 of the damaging insect ; l)ut it still remained to prove that 

 the suspected fly was the parent of the ova. I therefore 

 made a microscopic examination of the eggs which had been 

 deposited on the leaves ; these, under a power of 250 diam., 

 presented a beautiful reticulated structure. I then dissected 

 a number of the flies, whose abdomens were evidently dis- 

 tended with ova, with a view to compare the eggs in the 

 ovary with those I had already examined. I found them in 

 every stage of development, and discovered some of the exact 

 shape and size, though of softer consistency, than the eggs 

 on the leaves, and presenting the same network structure 

 characteristic of those which had been naturally excluded. 

 About this time I Avas made acquainted with Mr. Curtis's 

 description of the male of Anthomyia beta, which exactly 

 agreed Avith specimens I had taken myself, and as I also dis- 

 covered a couple of flies in coitu I could no longer have any 

 doubt on the subject. 



It appears singular that this is the first instance on record 

 of the mangolds sufi'ering to any extent from the depreda- 

 tions of these larvse ; the direct cause of the injury last year 

 being the large proportion of female flies compared with the 

 number of the males, being, on an average, as twelve to 

 one ; from the fact of the males only being hitherto recog- 

 nised, there can be little doubt that in former years this 

 sex predominated, hence the immunity of the plants from 

 injury up to this time ; but, as to the cause, whether atmo- 

 spheric or otherwise, of the large proportion of females during 

 the last year — this is a question which perhaps can never 

 be solved. The female fly continues to deposit ova quite 

 late in the season ; I found this to be the case as late as the 

 first week in November. I cannot think that the larvce 

 change to pupce in situ ; I never could detect a single pupa in 

 the leaf, and my observations, so far as they go, tend rather to 

 show^ that the maggots drop out from between the two cuticles, 

 and undergo their metamorphosis in the ground f" at any rate, 

 I could occasionally discover, by scraping away the soil, at the 



* While these pages were at the press, I Lave accidentally become ac- 

 quainted with three or four jmpcs ; I had placed fragments of leaves con- 

 taining larva; in a small cardboard box about two mouths ago, and on open- 

 ing tills (Dec. 17), I found that tlio larvte had assumed [\\ck fpa form, and 

 were loose in the box. 



