The Cabbage Root Maggot. 511 



How long the flies live in the summer is not known ; they lived 

 ten days in our cages in the iusectary. Doubtless they live but a 

 few days after providing for the perpetuation of the species. The 

 flies do no damage, for if they feed at all, it is only to eat a few 

 grains of pollen or to sip a little nectar from some flower. 



The immber of broods, and habits of the later broods. — It appears 

 to be the accepted belief among entomologists that there are three 

 or four generations or broods of this pest annually. In 1884, Dr. 

 Riley stated that ' ' the number of broods in the course of a season 

 has not been accurately followed in any given latitude, but there are 

 at least three. " Many authors have simply followed Bouche who 

 said in 1833, that there were several generations of the pest during 

 the summer. In 1874, Prof. Cook concluded that there were at 

 least two broods. 



A search through the earlier literature of the insect has revealed the prob- 

 able source of this idea that the pest passes through three or four genera- 

 tions annually. In 1865, Taschenberg said: "Because they (the flies) need 

 for iheir complete development, which begins with the early spring, on an 

 average eight weeks including ten days for the egg stage, therefore must 

 three complete generations in the course of a year be accepted as normal." 

 Thus, the number of generations has been merely a matter of calculation, 

 doubtless based on observations made only on the first brood in the spring. 



There is no doubt that a brood of flies appears early in the 



spring, in New York State in the latter part of April and the 



first week in May. These flies, and their progeny of maggots 



which work on the plants in May, constitute the first brood or 



generation of the pest. This brood appears, in greater or less 



numbers, in all localities where the insect occurs. And in most 



localities, in most seasons, both in Europe and America, it is the 



most destructive brood, working in early cabbages, radishes, 



cauliflowers, and turnips ; sometimes attacking these plants 



before they are removed from the seed bed. We also found this 



brood the most numerous on the weeds upon which it feeds. 



However, we find such statements as this from Dr. Fitch : "It is only 

 my earliest sown radishes, each year, from which I obtain any that are fit 

 for use, and for several years past, this first sowing has also been a total 

 failure." Mr. Fyles also says that the radish fly "appears in the end of 

 June and the beginning of July. I have found that radishes sown at Quebec 

 in the beginning of May " are a success. Thus, in some localities, especi- 

 ally in Canada, and in some years the first brood of the pest is not noticeably 



