CELEBY-STEM FLY. 17 



to a small extent, and probably only preying on decayed matter. This 

 was distinguishable by the caudal extremity not being rounded, but 

 rather slightly dilated, and furnished with numerous tubercles. To 

 make sure that this was not merely an early stage of the larva of the 

 P. apii, I examined a series of these in different stages of growth, and 

 found these, from the smallest (which might be about an eighth of the 

 size of the largest I had), all corresponding in structure. 



Circumstances prevented me, at the time, following up details of 

 life-history; but these will be found given at length by Prof. Westwood, 

 with figure of the fly, maggot, and other details, at page of 'Gardeners' 

 Chronicle ' for 1848, previously named. From these I may quote, 

 shortly, that Prof. Westwood found the maggots present in the Celery 

 in the month of February ; that these maggots turned, in the diseased 

 Celery stems (or in the earth in which they were placed), to chrysalids 

 or pupae, within an elongate oval case formed by the hardened maggot 

 skin ; and from these chrysalids the two-winged fly came out about the 

 middle of May. This fly he found to be very like the common Cheese 

 Fly. It was about three-eighths of an inch in spread of the wings ; 

 thorax and abdomen black ; head mostly chestnut colour ; legs very 

 pale straw colour, feet more dusky ; wings colourless, with veins very 

 pale buff. The body is described as sprinkled with fine golden 

 grey hairs. 



Pbevention and Remedies. — The observations of the past season 

 have added to those previously quoted, the certainty that there is a 

 summer generation, as I found specimens, only somewhere about the 

 sixteenth of an inch long , amongst those sent me at the beginning of 

 August. The second brood is presumably very soon developed from 

 chrysalids of these maggots, and if any measures could be taken to 

 destroy these it would save much mischief. 



For one thing, whether with summer or winter infested plants, a 

 rule, stringently carried out, that the plants were in no case to be 

 thrown to the manure heap, but burnt, or buried in wet manure, or so 

 treated that any chrysalids which might be in the stems should be 

 destroyed, would save some infestation. 



Where there has been a complete destruction of the plants by 

 infestation, probably a heavy dressing of gas-lime along the trenches, 

 and leaving the ground free until the air had neutralised the noxious 

 qualities, would destroy such chrysalids as might be in the earth. Or, 

 again, turning the earth well down into the trenches, and planting on 

 these some winter crop, which might be dibbled in, would at least 

 secure a return from the ground, though not in Celery, and would leave 

 the insect vermin buried safely down, out of the way of infesting 

 other plots, 







