1923 ENTOMOLOGICAL SOCIETY. 73 



over the North American continent. Its host plant is almost entirely the sun- 

 flower, both cultivated and wild. It has however, been found attacking Jeru- 

 salem artichokes (Helianthus tuber osus L). 



The sunflower fly is a true dipterous fly belonging to the family Trypetidse. 

 The general colour of the adult is yellow; a few black hairs on both the upper 

 and lower surface of the thorax; legs medium length resembling the body in 

 colour. The abdomen is a little narrower than the thorax, and is slightly darker 

 in appearance, owing to the numerous black hairs that cover it. On an average 

 the wings are seven m.m. long and three m.m. wide; the entire margin is 

 armed with small black bristles. The banding of the wings resembles somewhat 

 the letters "U F," as you may see from the specimens passed around. 



The time at which the first flies emerge would depend somewhat on the 

 temperature and moisture conditions. It would also vary in different localities. 

 At Port Stanley this summer the first fly was found on the 29th of May. The 

 maximum emergence was from June 3rd to June 14th; adults may, however, 

 continue to emerge up to August. Of all the flies throughout the season approxi- 

 mately 60 per cent, were females. The average length of life of the flies is 21 

 days, although some lived in cages for a much longer time. It was very difficult 

 to find out definitely the pre-oviposition period but it is believed to be about 

 13 days. 



Before laying the female moves from plant to plant in a very nervous and 

 restless manner until she finds a suitable spot. She then rises on her feet and 

 inserts her sharp sting-like ovipositor by repeated thrusts. The whole operation 

 requires from 30 to 40 seconds. 



In 14 feet of wild sunflower stalk there were 53 punctures and only 31 eggs, 

 showing that only 58.5 per cent, of the punctures contain eggs. 



The egg is very small, semi-transparent, almost elliptical, and about three 

 times as long as wide. It is perfectly smooth. The egg requires from five to 

 six days to hatch. 



The larva is cream coloured. The body consists of 13 segments and is 

 stout, tapering gradually to the anterior end. It is from seven to eight m.m. 

 long when full grown and 1.5 to 2 m.m. wide. 



The injury is caused by the larvae, They scratch the pith with two small 

 black hooks, and then suck up the juice, soon causing the pith to turn brown or 

 black. As the larvae grow they work towards the ground, and by the end of 

 the season in many stalks the whole of the pulp is eaten out, thus weakening 

 the stalk and causing many to fall over. On September 27th fully 1,400 stalks 

 were counted, and 10.4 per cent, of them had broken over. In many of the stalks 

 a mold sets in where the pulp has been destroyed. We tried to have the infested 

 stalks analysed to find the actual loss in food value. But the chemistry depart- 

 ment said that they could not determine that. 



Counts were also made of the seeds in the heads of the infested sunflowers. 

 Approximately 50 per cent, of the seeds were empty. Counts were also made 

 of the heads in uninfested stalks and 13 per cent, of the seeds were empty. This 

 shows that 37 per cent, of the seeds fail to develop, directly due to this fly. 



The maggots remain in the stalk from the time they hatch until the fall, 

 when they leave the stalk, and enter the ground to pupate. This year they began 

 to pupate the 8th of September, and all had left the stalks by the 21st of Septem- 

 ber. The larvae near the base enter the ground right through the stalk, while 

 others further up bore their way out wherever they are and drop to the ground . 



No control measures have as yet been worked out. At the California Experi- 

 mental Station attempts were made to control these flies with the hydrocarbons 



