The Ibaliidae are a small family of the superfamily Cynipoidea. Ibaliidae differ from most of the Cynipoidea by the larvae being on other wasp larvae in the group Siricidae. The Ibaliidae comprise three extant genera of fairly large , with a total of 20 species, and is a sister group to the rest of the Cynipoidea except the small subfamily Austrocynipidae.
Description
Their large size is a typical and obvious characteristic in the family, with lengths up to . The following distinct features are diagnostic characters, based on research by Ronquist
and Liu and Nordlander.
Body
The genae are swollen and pronounced. The female antenna consists of 11 segments, while the male antenna consists of 13 segments. A large portion of the
pronotum is well developed, called the dorsal pronotal area, with scutellar processes. The marginal cell of the forewing is elongated and thin. The gaster is long and pronouncedly compressed laterally. The seventh
tergum is large in females. An apical tubular process is present on the second
Arthropod leg of the hind leg. The
Arthropod leg is short, no longer than the
Arthropod leg.
| + Ibalia rufipes with Ibaliidae characteristics marked out
! Mesosoma
! Forewing
! Hind tarsus |
| | |
Reproduction and parasitism
The female lays the egg by
oviposition through the oviposition shafts created by
Siricidae, and the egg is deposited inside a
Siricidae larva.
In the species
Ibalia drewseni Borries,
Ibalia leucospoides (Hochenwarth) and
Ibalia japonica Matsumura, host detection by
Symbiosis fungus in the siricid has been observed.
The larva lives it in its first instars as an endoparasite, and later exits the host and lives on the remaining host tissues. The primary instar is polypodeiform with paired appendages on segments 1–12, and in the second to fourth , the appendages are lost. Until the terminal instar, the remaining Tail is gradually decreased.
The two subgenera of Ibalia differ in host choice, the subgenus Ibalia parasitizes coniferous-living Siricinae larvae and the subgenus Tremibalia parasitizes hardwood-living Tremicinae larvae. Few details are known about the genera Heteribalia and Eileenella, but both also parasitize wood-boring Siricidae.
Pest control
Several species in the genus
Ibalia have been introduced to South America, Australia, and New Zealand,
sometimes to control previous accidentally introduced Siricidae species parasitizing economically important pine forests.
Species used are, for example,
Ibalia leucospoides and
I. ensiger Norton. Results from introductions vary, and studies of long-term effects are lacking, but in some areas, the effects on pests have been successful; Siricidae populations have been strongly limited. They are most effective in combination with other parasitoid organisms, such as
.
Distribution and evolution
The Ibaliidae are concentrated to the Northern Hemisphere, the single species in
Eileenella found in Papua New Guinea is the only specimen reported to be naturally occurring in the Southern Hemisphere.
Ibalia is the most widespread and diverse genus, with the subgenus
Tremibalia concentrated in
China and the eastern
Palearctic realm, and
Ibalia in the western
Nearctic realm.
Heteribalia only occurs in
South Asia and
Japan. Phylogenetic analyses have indicated the Ibaliidae have spread from the eastern Palearctic and northern Asian regions in the early
Cretaceous.
An insect-parasitic life mode is probably ancestral in the Cynipoidea families, and the Ibaliidae are placed next to Austrocynipidae, as a sister group to Liopteridae, Figitidae and Cynipidae.
