228 MAINE AGRICULTURAL EXPERIMENT STATION. 1916. 



about a minute. The following is the rate at which ten suc- 

 cessive eggs were laid : 48 sec, 3 min., 2 min., 3 min., 4 min., 

 1 min. and 20 sec, 1 min., 1 min., 1 min., 1 min. 



The above eggs had practically all hatched over night pre- 

 vious to 8 A. M., August 16; the duration in the egg stage 

 having been about 4 days. 



On August 7 a number of females were found hovering 

 about among a very dense growth of rape on the Station farm. 

 Careful examination revealed an abundance of eggs, which 

 later proved to be this species, deposited on the under side of 

 the lower leaves near the ground where it was constantly wet 

 or damp. The eggs were ranked quite closely side by side in 

 groups of from 2 to 8, more commonly 4 or 5 (the sides of the 

 eggs touching each other). These eggs hatched August 11. 

 The larvae were apparently half -grown by August 23, and 

 began pupating August 31 to September 4. 



At the same time (August 7) a large number of larvae of all 

 sizes, and pupae in all stages of development, were found on 

 the under side of the leaves among the rape. The larvae appar- 

 ently sought out the moist places near the ground. These 

 plants were infested with Mysus pei'sicae but the aphids present 

 at this time were fewer in numbers than the predaceous larvae. 

 It seems to me likely that here is a case where an infestation 

 of aphids, which must have been severe to mature so many 

 hundreds of larvae, had been all but exterminated by the pre- 

 daceous larvae. This opinion gains confirmation from the fact 

 that many of the pupae present were undersized and somewhat 

 misshapen, such as often results from starving larvae. The 

 larvae collected were placed in all conceivable situations to see 

 if possibly they might feed on some other food ; but all foods 

 were refused except aphids . They showed a preference for 

 Mysus persicae and Aphis comifoliae from Cornus. Fed on 

 these aphids in captivity the larvae pupated between August 7 

 and 11, and adults or parasites emerged August 14 to 18. 



Of larvae collected August 16 two pupated August 24, one 

 emerging as adult August 28 the other August 31 ; another 

 pupated September 4 and emerged as adult September 9. 



Egg. (Fig. 30-7, 2, 3). Of the usual Syrphid shape, sub-cylindrical, 

 a little broader and more rounded at one end, narrower and truncated at 

 the micropylar end. The dimensions of 56 eggs from several different 



