Acgorium Sharkey & Quicke, 2020

Quicke, Donald L. J., Sharkey, Michael J., Janzen, Daniel, Hallwachs, Winnie, Hebert, Paul D. N. & Butcher, Buntika A., 2020, A new genus and species of Neotropical gregarious braconine parasitoid (Hymenoptera: Braconidae) of a caterpillar (Lepidoptera: Hesperiidae), Zootaxa 4816 (3), pp. 370-376 : 371-373

Acgorium Sharkey & Quicke gen. nov.

Type species: Acgorium felipechavarriai Sharkey n. sp.

Diagnosis. This ectoparasitic gregarious wasp differs from all New World Braconinae except for the Nearctic genus Lapicida Quicke in that Acgorium gen. nov. has a complete lamelliform midlongitudinal propodeal carina. It differs from Lapicida in that Acgorium has the median area of the metanotum smooth and without a midlongitudinal carina ( Lapicida has a complete midlongitudinal carina). More reliably, it differs from all other Braconidae or other insects by the distinctive COI DNA barcode and BIN of the holotype.

Description. Head: Terminal flagellomere pointed. Scapus slightly shorter ventrally than dorsally in lateral aspect. Dorsal margin of clypeus indicated by a groove, not carinate. Ventral margin of clypeus (above hypoclypeal depression) not produced. Labio-maxillary complex not elongate. Malar suture absent. Eyes glabrous. Frons flat behind antennal sockets, weak midlongitudinal carina extending from median ocellus to interantennal space.

Mesosoma: Mesoscutum smooth; notauli smooth, barely indicated, and not greatly converging posteriorly. Scutellar sulcus moderately wide, crenulate (with five crenulae). Median area of metanotum smooth without midlongitudinal carina. Precoxal sulcus absent. Propodeum smooth with well-defined midlongitudinal carina. Femora of normal dimensions. Length of hind tibia subequal to tarsus; without longitudinal lateral groove. Claws with a sharp to squared basal lobe.

Wings: Fore wing 2 nd submarginal cell narrowed apically, 3x longer than high at maximum lengths. Vein 1RS forming an angle of 45 degrees with C + SC + R. Vein (RS + M)a straight. Vein (RS + M)b as long as or slightly longer than m-cu. Vein 2CUa straight except for slight posterior angulation, not thickened posteriorly. Hind wing vein C+SC+R with one basal hamulus. Vein R short, as long as it is thick. Base of hind wing densely and evenly setose. Vein cu-a, reclivous, slightly curved. Vein 2-1A absent. Metasoma: Metasomal terga heavily sculptured with 8 visible terga, the last two of which are mostly concealed. Anterior surface of first metasomal tergum mostly vertical. First metasomal tergum with well-developed dorsal carinae that reach posterior margin separately, dorsope and laterope absent. Second tergum lacking mid-basal triangular area but with midlongitudinal carina and with pair of anterior, submedial raised, semicircular areas. Second suture deep and crenulate. Third tergum without demarked anterolateral areas. Terga 3-5 without subposterior transverse groove. Penultimate metasomal sternum heavily sclerotized and swollen apically. Ovipositor short, barely exerted, extremely slender, without obvious pre-apical dorsal nodus or ventral serrations.

Biology. The only species in our new genus, A. felipechavarriai , is a gregarious parasitoid of Dyscophellus phraxanor (Hesperiidae) feeding on mature leaves of Virola sebifera ( Figs 2 and 3 ). The host caterpillars of the other nine rearing records of this species, previously incorrectly called “ Bracon felipechavarriae ”, were feeding on this plant, V. koschnyi or Otoba novogranatensis (Myristicaceae) . All 2,105 rearing records of wild-caught D. phraxanor caterpillars are from ACG rain forest at intermediate elevations on the Caribbean slope of Cordillera Guanacaste, northwestern Costa Rica and have generated 72 parasitoid and hyperparasitoid rearings of other species of Tachinidae and Hymenoptera ( Janzen and Hallwachs 2016, 2019a).

Remarks/Relationships. The combination of an antennal scape shorter ventrally than dorsally (in lateral aspect), simple basal flagellomeres, and claws with large square or pointed basal lobe place the new genus in the Braconini . The combination of a complete lamelliform midlongitudinal propodeal carina, strong dorsal carinae of the first metasomal tergite, flexibly articulated junction between tergites 1 and 2, and six strongly sculptured meta- somal tergites suggests a possible relationship with the Plesiobracon Cameron group of genera (Achterberg 1983; Quicke 1988 ), a group that is otherwise only known from the Old World (almost entirely from the tropics). Most genera assigned to this group also have the mesoscutum densely and evenly short setose, but that character is absent in the new genus and partial in a few groups that appear on other grounds to be members of the Plesiobracon group ( Quicke 1988 ). Whether the Plesiobracon group is indeed monophyletic (with or without inclusion of the apparently closely-related Aspidobraconina (which share all their synapomorphies but additionally have tergites 1 and 2 fused) has not been tested yet with molecular phylogenetics. Therefore, another possibility is that the propodeal carina, strongly carinate first metasomal tergum, six heavily sculptured metasomal terga and short ovipositor are a syndrome of characters associated with some particular biological feature, such as an aspect of oviposition behavior. Interestingly, members of the Aspidobraconina as well as at least one member of the Plesiobracon group s.s. are parasitoids of butterflies (Rhopalocera) including Hesperiidae , but as endo- rather than ectoparasitoids (Gupta et al. 2016).

Etymology. Acgorium is named in honor of Área de Conservación Guanacaste, northwestern Costa Rica, to celebrate its 35 years of experimentation with converting a classical national park to a government-NGO hybrid collaboration for tropical biodiversity conservation through non-damaging biodevelopment ( Janzen and Hallwachs 2019b).

Figures

FIGURE 2. Last instar Dyscophellus phraxanor (Hesperiidae) caterpillar 09-SRNP-561 being exsanguinated and therefore killed by a brood of at least 29 presumed sibs of Acgorium felipechavarriai sp. nov. (09-SRNP-561-DHJ452257.jpg). These last instar wasp larvae continue to be attached and feed externally within the silked leaf shelter made by the caterpillar (non-infected caterpillars forage out on the leaf surfaces to feed at night). They are wet from exuded blood and perhaps other fluids.

FIGURE 3. Upper, group-constructed cocoon of Acgorium felipechavarriai sp. nov. spun tightly against the floor of the rolled leaf nest of a last instar Dyscophellus phraxanor (Hesperiidae) caterpillar (16-SRNP-30739-DHJ729848) feeding on mature leaves of Virola sebifera in mid-elevation tropical rain forest (ACG). While the wasp larvae spin the silk cocoon jointly (collaboratively), immediately after they make the “roof” they each spin their own individual cocoons below it, and escape through the individual-cut exit holes about 15 to 18 days later. The adult wasps immediately fly away with no sign of courtship or mating. It should be emphasized that the host larva shelters in the nest all day, but is fully exposed at night when feeding on open leaf surfaces. Once with visible larvae on its back, the host caterpillar becomes moribund in the nest but does not die until the group cocoon is spun. Lower, cadaver of the host caterpillar as semi-glued to the leaf next to the group (upper). It is not known if the group of larvae move slightly as a group prior to spinning the group cocoon, or just push the cadaver partly to the side in the process of spinning. The cadaver is not incorporated into the cocoon mass.