Notes on the genus Dendrocerus Ratzeburg (Hymenoptera, Megaspilidae) from China, with description of two new species

Species of the genus Dendrocerus Ratzeburg, 1852 (Hymenoptera: Megaspilidae) from China were studied. Six species are recorded, of which two known species, D. carpenteri (Curtis, 1829) and D. laticeps (Hedicke, 1929) are re-described; and two species are described as new to science, D. anisodontus Wang, Chen and Mikó sp. nov. and D. bellus Wang, Chen and Mikó sp. nov.. Sequences of the 28S rDNA were generated to associate both sexes of the same species.

Based on antennal characters, Dessart (1995) proposed five species-groups for Dendrocerus: halidayi, carpenteri, serricornis, punctipes and penmaricus (Bijoy and Rajmohana 2014). Species of the halidayi species-group generally have ramose antennae, but the D. mexicali species complex have moveable branches (Burks et al. 2016). The males of the D. halidayi species-group are characterized by their ramose antennae, and by the long branches on proximal 4, 5 or 6 flagellomeres. There are 22 species of this group worldwide (Pezzini et al. 2014). Two new species under D. halidayi speciesgroup, viz., D. bellus and D. anisodontus are hereby described and illustrated.

Materials and methods
This work is based upon the specimens in the following collections, with abbreviations used in the text: AHNU, Auhui Normal University, Anhui, China; IZCAS, Institute of Zoology, Chinese Academy of Sciences, Beijing, China; SYSBM, Sun Yat-sen University, The Museum of Biology, Guangzhou, China. Specimens were obtained from sweep nets, Malaise traps, and yellow pan traps.
Considering that sexual dimorphism is common in Dendrocerus, we sequenced the gene marker 28S rDNA to associate the female and male of the same species. Genomic DNA was extracted from a female and male of each putative species using a nondestructive DNA extraction protocol as described in Taekul et al. (2014). The primers for 28S amplification followed Zhang et al. (2008). Polymerase chain reactions (PCRs) were performed using a 25 μL system and conducted in a T100 Thermal Cycler (Bio-Rad). Thermocycling conditions were: an initial denaturing step at 94 °C for 1 min, followed by 35 cycles of 94 °C for 1 min, 50 °C for 30 s, 72 °C for 30 s and an additional extension at 72 °C for 5 min. Amplicons were directly sequenced in both directions with forward and reverse primers by GENERAL BIOL (Anhui, China). Chromatograms were assembled with Sequencing Analysis 6 (ThermoFisher Scientific, Gloucester, UK). All the amplified sequences were deposited into GenBank (see Table  1). The genetic distances were calculated using the Kimura 2-parameter (K2P) model in MEGA X (Kumar et al. 2018).
All voucher specimens were then point-mounted and air-dried. Photographs were taken with a Leica M205A stereomicroscope and a Leica DFC-500 digital camera, with extended focusing software. To prepare male genitalia for study, apical metasomal segments were removed from specimens and placed in 35% H 2 O 2 for 24 hours, 5% acetic acid for 24 hours, distilled water for one hour and then transferred to a droplet of glycerin on a concavity slide. Dissections were performed in glycerin by using #5 forceps and #2 insect pins.

Results
In the present paper, we describe two new species of Dendrocerus: D. anisodontus Wang, Chen and Mikó sp. nov. and D. bellus Wang, Chen and Mikó sp. nov., bringing the species number of this genus to six for China. The morphological re-description and photographs are provided for D. carpenteri and D. laticeps. No Chinese specimens of D. angustus and D. aphidum are available for this study.
Male Genitalia (Fig. 2): Genitalia with short cupula. Harpe median margin smooth and without tooth. Distal margin of harpe in lateral view blunt. Gonostipes longer than wide, fused dorsally; apical margin (part of gonostipes) with three teeth outward ( Fig. 2A). Median notch of distodorsal margin of gonostipes square. Female (Fig. 3): Body length: 1.8-2.1 mm. As for male except scape longer (scape about 1.3× longer than combined length of pedicel and F1). Pedicel and F1 approximately equal in length. Rest of flagellar segments short (L/B about 1.1-1.6), except F9 which is usually twice as long as broad. Flagellomeres flattened ventrally. Antenna black but distal end of pedicel sometimes lighter; weakly papillate, with short dense pubescence.
Etymology. The species name is a Greek masculine adjective meaning "unequal tooth", signifying the irregular branches of the antennae of males.
Distribution. China (Guangdong, Hainan, Sichuan, Yunnan). Etymology. The species name is a Latin masculine adjective meaning "beautiful and exquisite", signifying the beautiful coloration, especially in female.