Jwam. Pijls et al., INTERSPECIFIC INTERFERENCE BETWEEN APOANAGYRUS-LOPEZI AND APOANAGYRUS-DIVERSICORNIS, PARASITOIDS OF THE CASSAVA MEALYBUG PHENACOCCUS-MANIHOTI, Entomologia experimentalis et applicata, 78(2), 1996, pp. 221-230
The parasitoids Apoanagyrus lopezi De Santis and A. diversicornis (How
ard) (Hymenoptera: Encyrtidae) have been introduced into Africa for th
e biological control of the cassava mealybug Phenacoccus manihoti Mati
le-Ferrero (Homoptera: Pseudococcidae). We have studied competition be
tween these species to investigate if they can coexist. Here we report
on the influence of the simultaneous presence of non-conspecific adul
t females on searching efficiency on patches. Wasps of either species
foraged on discs of cassava leaf with mealybugs, while at the same tim
e different numbers of non-conspecifics were also depleting the patch.
Patch area per parasitoid and number of hosts available to each paras
itoid were equal in all treatments. In both species, the presence of o
ther foragers clearly affected several aspects of the parasitoids' beh
aviour. Patch residence time increased with the number of non-conspeci
fics in A, diversicornis. In both parasitoid species, the proportion o
f hosts left unparasitized after the patch visit decreased with increa
sing numbers of females on the patch. The proportions of super- and mu
ltiparasitism did not change with the number of females. Both species
produced more offspring during a patch visit in the presence of more n
on-conspecifics. These behavioural changes did not, however, lead to a
change in the offspring production rate on patches. A. diversicornis
produced offspring at a rate three times that of A. lopezi when one A.
lopezi and one A, diversicornis foraged simultaneously. This is the f
irst report of an aspect of interspecific competition where A. diversi
cornis has an advantage over A. lopezi. Interference between adult fem
ales thus promotes coexistence of the two species on P. manihoti.