Diadegma armillata (Gravenhorst, 1829)

Scaramozzino, Pier Luigi, Giovanni, Filippo Di, Loni, Augusto, Ricciardi, Renato & Lucchi, Andrea, 2018, Updated list of the insect parasitoids (Insecta, Hymenoptera) associated with Lobesiabotrana (Denis & Schiffermueller, 1775) (Lepidoptera, Tortricidae) in Italy. 2. Hymenoptera, Ichneumonidae, Anomaloninae and Campopleginae, ZooKeys 772, pp. 47-95 : 47

Diadegma armillata (Gravenhorst, 1829) Figure 6

Angitia tibialis : Silvestri 1912: 296; Leonardi 1925: 259.

Angitia (Dioctes) tibialis : Stellwaag 1928: 664.

Italian distribution of reared parasitoids.

Campania: Silvestri 1912.

Distribution.

Diadegma armillata is a Palaearctic widespread species. It is found throughout Europe, Middle East, Caucasus, Kazakhstan, China and Korea ( Yu et al. 2012; Zwakhals and van Achterberg 2017).

Host range.

It is an important koinobiont larval endoparasitoid of macro- and microlepidoptera ( Arctiidae , Argyresthiidae , Choreutidae , Coleophoridae , Gelechiidae , Geometridae , Gracillariidae , Lymantriidae , Noctuidae , Pieridae , Plutellidae , Psychidae , Pterophoridae , Pyralidae , Simaethidae , Tortricidae , Yponomeutidae ). Yu et al. (2012) list 57 host species. Further three species have to be added to the list: Celastrina argiolus (Linnaeus, 1758) ( Lycaenidae ), Acrobasis marmorea (Haworth, 1811) ( Pyralidae ) and Swammerdamia caesiella ( Hübner, 1796) ( Yponomeutidae ) ( Shaw et al. 2016).

Diadegma armillata is particularly active against various Yponomeuta spp., attacking crop fruits, and it was introduced in 1989-1991 from France to northwestern Washington (USA), to control the apple ermine moth, Yponomeuta malinellus (Zeller, 1838) without becoming established ( Unruh et al. 2003).

Ecological role.

Diadegma armillata is a multivoltine species. Silvestri (1912) obtained few specimens of this wasp from EGVM cocoons in Portici (Naples). The record of Silvestri remains the only one for this species on EGVM.

Taxonomic notes.

The first serious attempt to bring order in the existing confusion for the interpretation of the European species of the genus Diadegma Förster, 1869 is due to the efforts of Horstmann (1969), who revised many types of the described species. The identifications of most species were based on poor morphological characters and are unfortunately unreliable ( Horstmann 1969).

Diadegma armillata belongs to the subgenus Nythobia Förster, 1869, which includes group species with the seventh metasomal tergite deeply notched medially, the ovipositor sheath longer than the first metasomal tergite and shorter than the hind tibia ( Horstmann 1969). The female of D. armillata is distinguished from the related species by a head with strongly narrowed temples; last article of the antennae longer than wide; propodeum with area superomedia wider than long and opened posteriorly, costulae strong; petiolar area slightly sunken and transversely striated; first metasomal segment with slightly protruding spiracles and postpetiole with parallel sides; ovipositor sheath approx. twice the length of the first metasomal segment; front and middle coxae yellow, the middle ones sometimes darkened at the base; femora and tibiae reddish yellow; hind tibia externally dark brown with white-yellow spots at the base and in the middle; metasoma variably stained with red ( Horstmann 1969).

Some doubts regarding the distribution and host range of D. armillata arises from the fact that D. semiclausum (Hellen, 1949), a common parasitoid of the diamondback moth Plutella xylostella (Linnaeus, 1758), has been misidentified with D. tibialis (Gravenhorst, 1829), which is currently a synonym of D. armillata ( Horstmann 1969, Azidah et al. 2000). Under the name tibialis, D. semiclausum was introduced in 1951 from Italy to Australia to control the diamondback moth ( Oatman 1978).