African Arthropods/Wasps associated with plant galls

In the northern hemisphere, many plant galls are induced by wasps of the family Cynipidae, but this family is rarely encountered in the Afrotropics, where it comprises only four described species, all found in South Africa. In the Afrotropics, most gall-associated wasps are chacidoids.

Chalcidoidea associated with plant galls

Most chalcidoid wasps in the families Cynipencyrtidae, Epichrysomallidae, Melanosomellidae, Ormyridae and Tanaostigmatidae are associated with plant galls; their larvae and pupae develop within galls. Together, these families comprise the ‘Gall Clade’ within the Chalcidoidea.

In the Afrotropics four of these families are represented:

• Epichrysomallidae includes about 16 described Afrotropical species in seven genera; they are exclusively associated with figs (genus Ficus);
• Melanosomellidae has four known species in the Afrotropics, two of which were introduced from Australia for the biological control of invasive Australian wattle trees;
• Ormyridae is represented by three species of Asparagobius which form galls on Asparagus species, Halleriaphagus phagolucida, which forms galls on Halleria species, two species of Ouma (biology unknown), and 14 described species of Ormyrus, which are hyperparasitoids, attacking other gall-forming insects;
• Tanaostigmatidae contains five African species including Tanaostigmodes tambotis, which is phytophagous, forming galls on the stems of tamboti trees (Spirostachys africana); the biologies of the other species are unknown.

Ormyrus wasps on a Euclea stem gall

Ormyrus is a genus of parasitoid wasps with a worldwide distribution. Most species are thought to be hyperparasitoids, i.e. their larvae feed on the larvae of gall-forming insects; these galls are found on a wide variety of plants. These phtographs show the activity of Ormyrus wasps on a stem gall on a magic gwarrie (Euclea divinorum) shrub. In this case the gall-forming insect, and host of the Ormyrus parasite, is not known.

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  Male Ormyrus wasps on a stem gall, waiting for a female to emerge
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  Female Ormyrus wasp ovipositing into a stem gall
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  Stem gall on a Euclea divinorum shrub