Feb. 2. 1920 European Frit Fly in North America 459 



Eggs were obtained in a small proportion of cages, in from 20 to 40 

 per cent, as a rule. Many flies laid only i or 2 eggs, and the maximum 

 was about 10. Since the normal number of eggs maturing in the ovaries 

 of a female at one time is about 30, it is evident that the conditions 

 were far from satisfactory; but they were the only ones under which 

 any eggs were obtained. 



On account of the small number of eggs secured, each successive 

 generation in cages was much smaller than the preceding one. It is 

 therefore necessary to start the season with a large supply of material 

 to avoid running out before the end. With this species, though perhaps 

 not with related forms, it is easy to stock up with adults of the first 

 summer brood by placing considerable quantities of already infested 

 garden winter wheat under cages as early as June i. This wheat will 

 yield adults in the desired numbers to stock cages for the second brood. 

 Wheat taken from the fields is likely to be much less infested than that 

 sown in gardens; the latter therefore should be used for cages. 



Larvae on hatching from eggs in cages immediately entered the young 

 wheat stems and in most cases were allowed to develop there, the pot 

 being watered and kept under observation to see when the adults 

 made their appearance. For early larval stages, eggs were taken from 

 leaves and placed in a vial, where they could be examined more fre- 

 quently and closely than in the cage. In this way the newly hatched 

 larvae were obtained before they had fed. For later stages, larvae were 

 dissected out of wheat stems they had entered, placed on a fresh piece of 

 young stem, and corked up in a vial. Larvae so handled readily entered 

 the second stem, which would keep fresh for four or five days; 'a second 

 transfer would bring the larva to maturity — some, in fact, matured 

 without it. The process of dissecting the larva out was performed under a 

 low power of the binocular dissecting microscope, using a needle with 

 a minute hook at tip and slitting the stem carefully. This is a simpler 

 process than the description might indicate and was performed success- 

 fully hundreds of times with only a few mishaps. During the summer of 

 191 5 as many as 100 vials containing transferred larvae were under 

 observation at once. The vigor and endurance of the larvae are re- 

 markable. When the stems were left too long in the vials and decayed, 

 the larvae almost always survived. In several cases they endured 

 starvation for several days ; one fasted a week and then when given the 

 opportunity entered a wheat stem and in due time reached maturity. 

 They do not survive drying up, however, but require a moist atmosphere. 

 This is true also of the adults. 



WINTER brood: dates op spring emergence 



Records were kept in the spring of 191 6 on four cages containing 

 garden wheat that had wintered outdoors where it grew. The emergence 

 is shown in Table I. 



