Interspecific competition between Cephalonomia stephanoderis and Prorops nasuta (Hym.,Bethylidae), parasitoids of the coffee berry borer, Hypothenemus hampei (Col., Scolytidae)

The competition between Cephalonomia stephanoderis and Prorops nasuta was s tudied in the laboratory, using coffee fruits infested with the host of the se parasitoids, the coffee berry borer Hypothenemus hampei. Experiments wer e performed under different conditions, using: (a) three temperatures; (b) five densities of infested coffee fruits; and (c) introducing the parasitoi ds at different times. The effect of competition was determined according t o the production of the progeny. When cultured together at the same time, C . stephanoderis produced in general, more progeny than P. nasuta under cond itions of 29 degreesC and alternating temperatures of 18-29 degreesC. Never theless, there were significant differences at densities of 1.3. fruits : p arasitoids (F-0.05 = 8.9: d.f = 1, 12: P < 0.05) and 1 : 5 (F-0.05 = 7.56; d.f = 1, 12; P < 0.05) at 29 degreesC. Under alternating temperatures, ther e were differences at the same ratios as above in favour of C. stephanoderi s, 1 : 3 (F-0.05 = 20.08; d.f. = 1, 12; P < 0.05) and 1.5 (F-0.05 = 20.21; d.f. = 1, 12; P < 0.05). Prorops nasuta was clearly more successful in all densities at 18 degreesC. When C. stephanoderis is was introduced 10 days b efore P. nasuta, the progeny production was markedly higher in eight from 1 0 densities at temperatures of 29 degreesC and 18-29 degreesC. Despite bein g introduced 10 days later, P. nasuta showed better performance at 18 degre esC. When P. nasuta was introduced 10 days earlier than C. stephanoderis, t here were significant differences in progeny production in favour of P. nas uta in 13 of 15 fruit densities under the three temperatures. Both parasito ids avoided ovipositing on previously parasitized hosts. Aggressive behavio ur or interference was not observed when they were outside coffee fruits.