Jp. Michaud et B. Belliure, Impact of syrphid predation on production of migrants in colonies of the brown citrus aphid, Toxoptera citricida (Homoptera : Aphididae), BIOL CONTRO, 21(1), 2001, pp. 91-95
Colonies of the brown citrus aphid, Toxoptera citricida (Kirkaldy), were st
udied in the laboratory with and without larval predation by the syrphid Ps
eudodorus clavatus (F.). Syrphid larvae fed for a mean of 8 days and the si
ze of aphid colonies was significantly reduced compared to controls at day
4 after onset of feeding to day 9 inclusively. Colonies that survived preda
tion by syrphid larvae grew to be as large as control colonies. Control col
onies matured alatae earlier than did colonies subjected to actual or simul
ated predation. Significantly more reproductive apterae emigrated from cont
rol colonies than from those in the actual and simulated predation treatmen
ts and the emigration occurred significantly earlier. The lack of differenc
es between paired T. citricida colonies in the actual and simulated predati
on treatments suggests that the only measurable effect of syrphid predation
on aphid colonies was density reduction. There was substantial variation i
n aphid colony success (=production of migrants) within treatments. Both ap
terous and alate nymphs often failed to mature and late-maturing apterae fa
iled to reproduce or emigrate. The results indicate that colonies of T. cit
ricida that experience predation, whether real or simulated, suffer a delay
in the production of alatae and produce fewer apterous migrants than colon
ies that escape predation. (C) 2001 Academic Press.