Different impacts of two species of aphid-attending ants with different aggressiveness on the number of emerging adults of the aphid's primary parasitoid and hyperparasitoids

The impacts of two species of ants (Lasius niger and Pristomyrex pungens) attending the cotton aphid (Aphis gossypii) on the number of emerging adults of the aphid's primary parasitoid (Lysiphlebus japonicus) and hyperparasitoids were assessed experimentally at a no-pesticide mandarin grove. L. japonicus females were observed foraging frequently in aphid colonies attended by either ant species, with more females in P. pungens-attended than in L. niger-attended colonies, but rarely in aphid colonies where ants were artificially excluded. Females were less often attacked by P. pungens workers than by L. niger workers, so that they stayed longer and oviposited into more aphids in P. pungens-attended than in L. niger-attended colonies. Attendance by each ant species reduced predator numbers in aphid colonies, compared to colonies where ants were absent, although P. pangens was slightly less effective in repelling predators. Therefore, both ant species incidentally protected parasitized aphids from predators. Consequently, L. japonicus-mummies were abundant in colonies attended by either ant species, with more mummies in P. plingens-attended colonies, and were scarce in ant-excluded colonies. The hyperparasitism and predation on L. japonicus larvae within mummies occurred more frequently in P. pungens-attended than in L. niger-attended colonies, but mummy predation rate was only 20916 in the former. As a result, the number of emerging L. japonicus adults did not differ significantly between aphid colonies attended by the two ant species, but significantly more hyperparasitoids emerged in colonies attended by the relatively less aggressive P. pungens than in colonies attended by L. niger.