''Trichilogaster signiventris'', commonly known as the golden wattle bud-galling wasp, is a species of Australian

chalcid wasp Chalcid wasps (, , for their metallic colour) are insects within the superfamily Chalcidoidea, part of the order Hymenoptera. The superfamily contains some 22,500 known species, and an estimated total diversity of more than 500,000 species, m ...

s that parasitises, among others, ''

Acacia pycnantha ''Acacia pycnantha'', most commonly known as the golden wattle, is a tree of the family Fabaceae native to southeastern Australia. It grows to a height of and has phyllodes (flattened leaf stalks) instead of true leaves. Sickle-shaped, thes ...

'' (golden wattle). It has been introduced into

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...

, where the golden wattle has become an

invasive pest An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

. American entomologist

Alexandre Arsène Girault Alexandre Arsène Girault ( ; 9 January 1884 – 2 May 1941) was an American entomologist specializing in the study of chalcid wasps. An eccentric and controversial figure, Girault was also a prolific and dedicated entomologist. He published mo ...

described the species as ''Perilampella signiventris'' in 1931. The female is yellow and black in colour, though highly variable in colour proportion and pattern. It is long. The male is of similar size and almost entirely black with black and yellow legs. The success of the related species ''

Trichilogaster acaciaelongifoliae ''Trichilogaster acaciaelongifoliae'' is an Australian bud-galling wasp from the family Pteromalidae that parasitises, among others, ''Acacia longifolia'' (long-leaved wattle, or Sydney golden wattle), which has become an invasive pest An ...

'' in managing ''

Acacia longifolia ''Acacia longifolia'' is a species of ''Acacia'' native to southeastern Australia, from the extreme southeast of Queensland, eastern New South Wales, eastern and southern Victoria, and southeastern South Australia. Common names for it include l ...

'' led scientists to look for another species to control ''A. pycnantha''. ''T. signiventris'' was introduced twice and at first thought a failure. Wasps from Lake Natimuk in Victoria were transported and released in

Western Cape The Western Cape is a province of South Africa, situated on the south-western coast of the country. It is the fourth largest of the nine provinces with an area of , and the third most populous, with an estimated 7 million inhabitants in 2020 ...

in 1987 and as no

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external Tissue (biology), tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissu ...

s were seen the first summer, a second transfer — this time from

Mount Compass, South Australia Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, C ...

— was made in 1992 as scientists suspected the first cohort might have been incompatible with populations of golden wattle in Africa. The host species are golden wattle (''Acacia pycnantha'') and ''

Acacia rivalis ''Acacia rivalis'', commonly known as silver wattle or creek wattle, is a shrub or tree belonging to the genus ''Acacia'' and the subgenus ''Phyllodineae'' native to southern Australia. Description The obconic shrub or tree typically grows to a ...

''. The eggs are laid by short-lived adult wasps into buds of flower heads in the summer, before hatching in May and June when the larvae induce the formation of the grape-like galls and prevent flower development. The galls can be so heavy that branches break under their weight. It has reduced the capacity of trees to reproduce throughout their range. It is possible that the galls also reduce the resilience of the host plants by absorbing nutrients and hence starving them. The galls are up to in diameter and contain several grubs.

References

{{Taxonbar, from=Q13935597 Pteromalidae Insects used for control of invasive plants Biological pest control wasps