THE RED SPIDER ON COTTON. 



'55 



demonstrations of the economic value of the species have been seen 

 in the field that it holds a position of greatest importance as an 

 enemy of the red spider. Duffey records chrysopid larvse as pre- 

 dacious on the pupse of this form, and we also have observed lace- 

 wing-fly larvae devouring the immature stages. 



Stethorus utiUs Horn. — This little brownish species has been ob- 

 served in red-spider colonies on cotton. It is second m importance 

 only to the preceding ladybird, and is most in evidence during July 

 and August. An individual of this species (in the third instar) was 

 observed to eat 3 mite eggs in 7, 7f , and 8 seconds. This is the 

 fastest rate of egg destruction noted for any predator. Another 

 individual (in the fourth instar) sucked 4 mite eggs in 28, 72, 46, and 

 77 seconds. Two larvae were isolated and kept supplied with red 

 spider eggs. One escaped, but the other was reared through to 

 adult. Table XXII gives the life-history record of this individual. 



Table XXII. — Life cycle of Stethorus utilis, Batesburg, S. C. (Individual No. 1.) 



Eggs collected July 25 



Eggs hatched July 29 



First molt Aug. 1, 9 a. m. 



Second molt Aug. 2, 11.39 a. m. 



Third molt Aug. 4, 3 p. m. 



Pupated Aug. 9, 9 a. m. 



Adult issued Aug. 13, 9 a. m. 



Length of incubation 4 days (?) 



Length of first instar 3 days 



Length of second instar 1^ days 



Length of third instar 2-|- days 



Length of fotuth instar 4| days 



Pupal period 4 days 



Deposition to adult 19 days (?) 



Since the conditions surrounding this individual were as nearly 

 normal as possible, it is probable that the foregoing record represents 

 fairly the hfe cycle of the species. 



Table XXIII contains statistics covering the entire feeding 

 capacity of one individual of this species from hatching until adult. 



Table XXIII. — Consumption of red-spider eggs by Stethorus utilis. 



Hatched July 29. 



Eggs eaten : 



First day 10 



Second day 14 



Third day 7' 



Fourth day 32 



Fifth day 38 



Sixth day 17 



Seventh day 38 



Eighth day 73 



Ninth day 40 



Eggs eaten — Continued. 



Tenth day 1 116 



Total 385 



Feeding days 10 



Average daily consumption 



Eggs eaten : 



During first instar 



During second instar 



During third instar 



38.5 



31 



32 



Durin'j: fourth instar 2G7 



' Was found piipato'l on (ilevonth day. 



It will bo seen that the above; indivichial in 10 feeding days ato 385 

 rod-spider eggs, or 38.5 eggs per day. Altliough this coccinc^llid has 

 frequently been seen eating mites in outdoor locations, tlie cxperi- 

 irnailiil indivlduid was confined to un cx(Iusiv(! o<r<f: di(^t, in ord(ir to 



