EXPERIMENT STATION BULLETINS. 



187 



Fig. 37. — Onion-mascot, adult fly, enlarged. 

 Original. 



REMEDIAL. 



The remedial measures consist 

 in riepelling the adult flies that 

 come to lay their eggs and in 

 stimulating the young plants to 

 very vigorous growth by means 

 of commercial fertilizers and cul- 

 tivation. Pull out and destroy 

 the young plants as soon as they 

 show the presence of the pests, 

 and do evcrjthing possible to 

 stimulate the plants to rapid 

 growth. The best repellant thus 

 far discovered is carbolic-acid 

 emulsion, diluted thirty times, 

 and applied with a sprinkler. 

 The formula for this is given in 

 the directions for making in- 

 secticides. It will be necessary 

 to repeat the application at in- 

 tervals of about a week, but good 

 work early in the season is sure 

 to count in reducing the num- 

 bers of the flies later on. 



Barred-winged Onion-maggot (Chaetopsis aenea). 



Once a deceiver, always distrusted, applies to this dainty and really 

 very pretty little fly' The adults of this insect are commonly seen sit- 

 ting on corn or reed grass, sunning themselves and darting about, appar- 

 ently for sheer enjoyment. From time to time, however, disquieting 

 rumors have come in; accusations of transgressions in the wheat and 

 oat fields, in the corn and the sugar-cane. Such reports naturally un- 

 dermine the standing of our fraud, and it only remained for the accused 

 to attack the onion crop in 1901, to prove his double dealing and to set 

 the hand of man against him, at least in the regions of the rich muck 

 land in the south-central part of the State where such quantities of 

 onion seed are raised. On this occasion hundreds of bushels of onions 

 were destroyed, rotted after harvest or were so wormy at harvest time 

 that they were worthless. Since that time the pest has been so cir- 

 cumspect that we are able to prove nothing against it, although the 

 rearing of adults from a large enough lot of samples, would likely bring 

 some of the flies to light. 



The flies themselves are about three-sixteenths of an inch in length 

 and, with the wings at rest, about one-fourth of an inch from the front 

 of the head to the tips of the wings. In color, the back is metallic blue- 

 green except the head which is mostly hoary, with brownish-black eyes. 

 The wings are transversely crossed by three smoky bands, the outer 

 two coalescing at each end.. 



In our cages, the winter was passed in the onions, the maggots chang- 

 ing to pupae in the autumn, and the flies emerging early in the spring. 



