Trichrysis Lichtenstein, 1876

Rosa, Paolo, Aswathi, Pokkattu Gopi, Wiśniowski, Bogdan & Bijoy, Chenthamarakshan, 2022, Preliminary revision of the Indian cuckoo wasp genera Trichrysis Lichtenstein, 1876 and Chrysidea Bischoff, 1910, with description of a new species (Hymenoptera, Chrysididae), European Journal of Taxonomy 852, pp. 117-143 : 119-121

Genus Trichrysis Lichtenstein, 1876

Trichrysis Lichtenstein, 1876: 27 .

Type species

Sphex cyanea Linnaeus, 1758: 572 [= Trichrysis cyanea ( Linnaeus, 1758) ].

Diagnosis

Head broader than high; scapal basin concave, striate, or punctate; TFC various, usually single and medially raised, sometimes double, down curved along eye margin, or with branches upward extended to ocellar area; MS usually about 1 MOD; pronotum with distinct and complete sublateral carina, sometimes incomplete or weak, faint in the inops species group; mesopleuron with broad episternal and scrobal sulcus; metasoma with geminate punctures; T2 usually with median carina; T3 with three or five teeth; lateral teeth in some species can be merely angle-shaped; S2 with black spots usually fused medially, rarely separated by a narrow line, or largely separated in the inops group, however, never connected to anterior or lateral margins.

Members of this genus are usually completely blue or green in colour, but a few Indian and African species have red markings, in particular on the metasoma; small males can often be blackish dorsally.

The genus Trichrysis is currently subdivided into three heterogeneous species groups: the cyanea , inops and lusca groups ( Rosa et al. 2016).

Indian members are subdivided in the following groups:

• lusca group: Trichrysis bengalensis ( Mocsáry, 1889) T. imperiosa ( Smith, 1874) , T. lusca ( Fabricius, 1804)

• cyanea group: Trichrysis excisifrons ( Mocsáry, 1912) , T. lanka ( Bingham, 1903) , T. poseidonia sp. nov., T. tonkinensis ( Mocsáry, 1914) , T. triacantha ( Mocsáry, 1889)

• inops group: Trichrysis inops ( Gribodo, 1884) , T. scioensis ( Gribodo, 1879)

Hosts

Hosts are cavity-nesting crabronid and pompilid wasps ( Pärn et al. 2014; Paukkunen et al. 2015; Pauli et al. 2019). Additionally, cavity-nesting solitary bee species have been reported in the old literature as hosts (e.g., Trautmann 1927), but these records should be considered unreliable due to the very different biology of bees compared to crabronid and pompilid hosts.

Distribution

The genus includes more than 40 species distributed in the Palaearctic, Afrotropical, Australian, and Oriental Regions ( Bohart 1988; Rosa et al. 2016, 2021a; Wiśniowski et al. 2020).

Differential diagnosis

In the Old World, some members of Trichrysis can easily be confused with members of the genus Chrysidea . Linsenmaier (1987) synonymised Chrysidea with Trichrysis (as a subgenus of Chrysis ), but the genus Chrysidea was later considered as valid and separate by Bohart (1988) and Kimsey & Bohart (1991). The recent phylogeny by Pauli et al. (2019) shows a close affinity between these two genera, which are well identified in a subordinated clade. However, considering the position of these two genera within the Chrysis lineage, the authors suggested combining both genera with Chrysis Linnaeus, 1761 . We support the point of view of Pauli et al. (2019); however, waiting for a revision of the Chrysidini classification, we still consider the two genera separately.

A combination of morphological characteristics allows the separation of Trichrysis and Chrysidea ( Table 1 ): sublateral carina (present in Trichrysis vs faint or rarely present in Chrysidea and in some species of the inops group); black spots on the second sternum (medially fused or nearly so in Trichrysis vs distinctly separated by 1–2 × MOD in Chrysidea and the inops group); number of teeth on the apical margin of the third tergum (three or five in Trichrysis , sometimes lateral ones barely visible like angles vs two lateral teeth, medially straight, weakly undulate, or rarely with a median tooth in Chrysidea ); transverse frontal carina (variable in Trichrysis , anyway not topping the scapal basin, vs topping the scapal basin in Chrysidea ); medial cell [= discoidal cell in Kimsey & Bohart 1991] (complete in Trichrysis , Chrysidea falsa and C. mendicalis vs incomplete in the other members of Chrysidea , with its outer veins either not or only partly sclerotised); genital capsule (gonocoxa shortened with distinct, elongate gonostylus vs gonocoxa fully developed without distinct gonostylus); body colours (green and blue in both genera, yet some species of Trichrysis have red, golden or bronze spots, stripes, or highlights which are not recorded in Chrysidea ).

Rosa et al. (2021a) recently published a checklist of Indian cuckoo wasps, with a key for the identification of known and expected genera for the country.