Larissimus nigricans Carrington-Hoekstra & Whitfield, 2023

Carrington-Hoekstra, Pomona, Fernandez-Triana, Jose, Dyer, Lee A. & Whitfield, James, 2023, Larissimus nigricans sp. nov. (Hymenoptera, Braconidae), a new reared species of a rare neotropical genus recovered through biodiversity inventory in Ecuador, ZooKeys 1156, pp. 15-24 : 15

Larissimus nigricans Carrington-Hoekstra & Whitfield sp. nov.

Fig. 1A-F

Description.

Holotype male. Body length 5.5 mm: fore wing length 5.4 mm.

Color (Fig. 1A ). Dark chestnut-brown, nearly black except: lighter brown clypeus, labrum, lateroventral portions of pronotum and propleuron, hind margin of propodeum, most of fore and mid legs and hind femur; whitish palpi, mid coxa, distoventral portions of hind coxa, anterior half and posterior margin of first metasomal tergite and lateral portions of metasomal tergites and sternites.

Head (Fig. 1B, C ). Antenna slender and roughly same length as body; placodes on flagellomeres roughly arranged in somewhat disorganized rows (typically three proximally). Face and eyes moderately setose, less so in an area posterior to the antenna and anterior to the ocelli. Labrum large and contrastingly colored (pale against a dark frons), with indentation dividing the labrum into a smaller dorsal section and larger ventral section. Ocelli arranged in low triangle (anterior edge of lateral ocelli on more or less same transverse line as posterior edge of anterior ocellus); lateral ocellus slightly truncated laterally due to overlapping cuticle.

Mesosoma (Fig. 1A, C, D ). Pronotum laterally mostly smooth and hairless with setae mostly confined dorsal portion; ventral groove broad and smooth, dorsal groove indistinct. Mesoscutum convex, nearly smooth over most of surface with denser setae and faint punctation anteriorly and laterally. Scutellum smooth, convex, and subtriangular. Mesopleuron hairless centrally, with smooth shallow concavity in posterior half. Propodeum smooth with sharply defined medial carina over entire length.

Wings (Fig. 1E ). Fore wing areolet of moderate size, strongly triangular. Vein 2r exiting the pterostigma at nearly a right angle (vs much more strongly angled to distal end in L. cassander ) and straight to juncture with 1Rs. Height and length of triangular areolet nearly equal. Hind wing: Cu and cu-a bending slightly distally/ ”outward” at juncture with M + Cu. Vein 3M as strong as 2M. Vein r vaguely spectral or absent. 2r-m weak, unpigmented.

Legs (Fig. 1A, D ). Middle leg: inner tibial spur much longer than outer and nearly as long as basitarsus. Hind leg: proximal end of femur marked with a very narrow light band (matching trochanter); tibial spurs both long, inner longer than outer and roughly 0.75 as long as basitarsus.

Metasoma (Fig. 1D , known only from male): tergite I smooth, more than twice as long as broad (narrowest just before midlength), with medial groove strongest anteriorly. Tergite II smooth, strongly triangular and longer than maximum width, more than twice as broad posteriorly as anteriorly. Laterotergites strongly whitish and matching lateral band of white on Tergite III and more posterior tergites. Tergite III rectangular over posterior half but with anterolateral corners angled; central third polished and slightly raised and set off from more setose lateral portions by longitudinal grooves. Tergites IV-V roughly rectangular with a small medial patch of hairlessness surrounded by light setae.

Female. Unknown.

Variation.

The two males available are extremely similar despite arising from different rearings in different years. The paratype male is slightly larger than the holotype.

Cocoon

(Fig. 1F ). White, bluntly oval, spun from dense silk with loose strands externally.

Hosts.

Unidentified species of Ardonea Walker ( Erebidae , subfamily Arctiinae , tribe Lithosiini ) caterpillar (Fig. 2A, B ) feeding on Chusquea scandens Kunth ( Poaceae ), a common and widespread Andean bamboo (Fig. 2C ).

Material examined.

Holotype male: Ecuador: Napo Prov., Yanayacu Biological Station , bamboo trail 2051, -0.5833, -77.8978, 218 m elev., collected 12 February 2011, rearing code 55036 . Paratype: same data as holotype but collected on yy road 2100, -0.5667, -77.8667, 21 April 2009, rearing code 38108. Both holotype and paratype deposited in Canadian National Collection of Insects, Ottawa (CNC) .

Etymology.

From the Latin “nigricans”, meaning “blackish”. JFT and JBW have seen additional undescribed species of Larissimus (primarily in the Canadian National Insect Collection) with different color patterns, but not predominantly blackish ones.

Comments.

Despite the dramatically different color combination and pattern, this new species is not strikingly different morphologically from L. cassander , at least based on the two males we have seen. Most structural differences are in minor shape proportions of structures (metasomal tergites narrower in the new species) and in wing vein angles (e.g., as mentioned above, compare angle of 2r in Figs 1E , 3C ).

Molecular data.

Cytochrome c oxidase subunit 1 barcode sequence (sequence code BCNCC047-22 in the Barcode of Life (BOLD) database ( Ratnasingham and Hebert 2007, 2013) consists of 614 bp and is 12% different in base pair identity from that of L. cassander (BOLD BIN BOLD:ABU6476).

Figures

Figure 1. Larissimus nigricans sp. nov., male A lateral habitus B proximal regions of left antenna C dorsal view, head and mesosoma D dorsal view, propodeum and metasoma E wings F emerged cocoon.

Figure 2. Host and host plant of L. nigricans sp. nov. A parasitized caterpillar of lithosiine (Arctiinae, Erebidae) moth on Chusquea leaf B unparasitized caterpillar of the same species, showing healthy color, and from which the adult was reared and identified as Ardonea sp. C a stand of Chusquea scandens Kunth from which the host caterpillars were reared.

Figure 3. Larissimus cassander Nixon, male, Brazil A lateral habitus B head, frontal view C fore wing D head, view from left side, showing malar suture E dorsal view, head and mesosoma F dorsal view, metasoma.