Four new species of the genus Carinostigmus Tsuneki (Hymenoptera, Apoidea, Crabronidae) from Oriental China, with an updated key to the Chinese species

The taxonomy of the apoid wasps of the genus Carinostigmus from China is studied, with description of four new species, namely Carinostigmus capiconvergens Bashir & Ma, sp. nov., Carinostigmus longivertex Bashir & Ma, sp. nov., Carinostigmus rugipunctatus Bashir & Ma, sp. nov., and Carinostigmus triangularis Bashir & Ma, sp. nov. An updated key to the Chinese species of Carinostigmus is provided.


Introduction
Carinostigmus was described by Tsuneki (1954) as subgenus of Stigmus Panzer, 1804, and was elevated to genus level by Bohart and Menke (1976). Carinostigmus belongs to the subfamily Pemphredoninae and currently comprises of 40 species and one subspecies worldwide. A huge diversity is found in the Oriental region with 23 species, followed by Afrotropical realm with 11 species and one subspecies; two species in this diversity are distributed across Palearctic region and four species are both Palearctic and Specimens were examined with an Olympus stereomicroscope (SZ Series) with an ocular micrometer. The images were taken with a Keyence VHX-5000 digital optical microscope (camera with resolution of 1600 × 1200 pixels), and edited with Adobe Photoshop 8.0. Measurements and ratio were acquired using an ocular scale on Olympus stereo microscope SZX2-TR30 at 2× and 5.4× magnification, respectively.
For terminology, we mainly followed Bohart and Menke (1976), Harris (1979), and Bashir et al. (2020). The descriptions are based on the holotypes only, and paratypes displaying some variation are given in square brackets in detail.
Male. Unknown. Distribution. China (Yunnan). Etymology. The name, longivertex, is derived from the Latin words longus (= long) and vertex (= vertex), referring to the very long vertex, with the ocello-occipital distance (OCD) being four times as long as postocellar distance (POD), 29 : 7. A noun in apposition.

Diagnosis.
This new species can be separated from all other Carinostigmus species from China by the following character combinations: mandible reddish brown basally; legs largely fulvous; labrum truncate apically; free margin of median lobe of clypeus broadly produced; median frons rugulose; occipital carina broad, without foveolate; lateral angles of pronotal collar not projected; metanotum smooth medially; propodeum with large smooth area medially; petiole dorsal with irregularly weak rugae basally; pygidial area depressed. It is closely related to C. congruus (Walker) 1860, but differs from it in the following characters (states of C. congruus in brackets): inter-antennal tubercle without T-shape at apex (inter-antennal tubercle with T-shaped at apex); inner orbital furrow inconspicuously foveolate (inner orbital furrow distinctly foveolate); pronotal ridge strongly marked (pronotal ridge weakly marked), slightly emarginate in middle (not emarginate in middle); occipital carina broad as Fig. 4B (occipital carina narrow as Fig. 3B); lower gena with dense, sturdy, longitudinal rugae medially (lower gena without rugae medially); notaulus inconspicuously grooved, extending to one third of scutum length (notaulus strongly impressed, extending to anterior ¼ of scutum length); propodeum with smaller smooth area than C. congruus; petiole dorsal with few irregularly weak rugae basally (petiole dorsal without rugae); petiole laterally smooth (petiole laterally with a few weak carinae or smooth) and pygidial area u-shaped (pygidial area oval shaped).
Male. Unknown Distribution. China (Yunnan). Etymology. The name, triangularis, is derived from the Latin word triangulus (= triangle), referring to the triangular shape of the labrum.