52 



BULLETIlsr 416, U. S. DEPAETMENT OF AGEICULTTJRE. 



determine the egg-eating capacity of Mycodiplosis, but from a few 

 field observations we are convinced that its appetite is about the same 

 as that of Arthrocnodax Carolina. 



Syrphidae. 



Quayle (1913) states that there are two or three species of syrphus- 

 fly larvae that eat red spiders. Ewing (1914) also records that he 

 has seen them feeding on the mites in hop fields. However, we find 

 no records of any of these having been reared or specifically identified. 



At Batesburg syrphus flies are found in all stages in cotton fields 

 from the last of May until the 1st of September, and are most 

 abundant during July and August. They are incidental enemies of 

 the red spider, and are more intent upon the capture of aphids and 

 insects more conspicuous than mites. However, they are often seen 

 crawling through red-spider colonies, and upon a few occasions 

 have actually been seen to devour adult mites, 



Baccha clavata Fab. — This dark-colored, waspHke syrphid was 

 apparently the commonest species. The larvae and the large, flesh- 

 oolored puparia could always be fouQd through the midsummer on 

 cotton infested with aphids and mites. A larva was seen to grasp 

 and devour a female red spider in an interval of 2 or 3 seconds. 

 Table XXI gives statistics on red-spider consumption gathered from 

 tests with larvae of Baccha clavata collected in the field in various 

 stages of development. 



Table XXI. — Red-spider consumption by larvx of Baccha clavata, Batesburg, S. C. 



Individual 

 No. 



Consumption of mites, i 



■1st 

 day. 



2d 

 day. 



3d 

 day. 



4th 

 day. 



5th 

 day. 



6th 

 day. 



7th 

 day. 



1 



8th 9th 

 day. day. 



10th 

 day. 



Feed- 

 ing 

 days. 



Total 

 mites 

 eaten. 



1 



19 

 70 

 60 

 20 

 13 

















1 

 2 

 10 



1 

 3 



19 



126 



253 



20 



32 



2 



2 56 

 33 















3 



47 



2 



26 



13 21 



27 1 20 



4 



4 



5 



10 



9 









Total . . 



I 1 ' 







1 



! 











17 



450 





1 1 



1 







! 





1 Fed with adult mites but many mite eggs were also eaten. 



2 Pupated. 



It will be seen that 5 larvae of BaccJia clavata in 17 feeding days 

 consumed 450 adult red spiders, which gives an average of 26.5 

 mites per day. 



ATlogra])ta obliqua Say. — This medium-sized syrphus-fly, with 

 abdomen alternately banded with sulphur yellow and chocolate 

 brown, probably ranks second in abundance among these flies. Its 

 larvae are seen commonly in fields during August. 



