﻿ Tricosauniseriata, a new species of xyleborine ambrosia beetle from Thailand (Coleoptera, Curculionidae, Scolytinae, Xyleborini)

﻿Abstract A new species, Tricosauniseriatasp. nov., is described here. A list of Tricosa species found in Thailand with distributions and an updated key to Tricosa are also provided.


Introduction
The xyleborine ambrosia beetle genus Tricosa Cognato, Smith & Beaver, 2020 (Curculionidae, Scolytinae) contains six species Smith et al. 2022). Two species were originally described as Xyleborus Eichhoff, 1864 and Cyclorhipidion Hagedorn, 1912, and four species were subsequently described Smith et al. 2022). Tricosa shares diagnostic characters with three xyleborine genera, Cyclorhipidion Hagedorn, 1912, Cryptoxyleborus Schedl, 1937, and Fraudatrix Cognato, Smith & Beaver, 2020 including either a setose and/or an attenuate appearance. Tricosa is distinguished from Cyclorhipidion by the slightly tapering elytra, from Cryptoxyleborus by the obliquely triangular protibial and attenuate elytra, and from Fraudatrix by the four-segmented antennal This publication S: Narathiwat funicle, the type 3 antennal club with one or two sutures visible on the posterior face, and the pronotal disc being as long as or shorter than the anterior slope .
Tricosa species are mainly distributed in southern Asia and eastern Papua New Guinea Smith et al. 2020Smith et al. , 2022. Three species have been previously recorded from Thailand, Tricosa cattienensis , T. indochinensis Cognato, Smith & Beaver, 2020, and T. metacuneolus (Eggers, 1940 (Beaver et al. 2014;Cognato et al. 2020). In this present study, we describe a new species, increasing the number of Thai Tricosa species to four and adding a seventh member to the genus (Table 1).

Materials and methods
A specimen was collected from a small branch of Artocarpus integer (Moraceae) in the lowland tropical rain forest of the Hala-Bala Wildlife Sanctuary, Narathiwat province, Thailand. Photographs were taken with a Canon 5D digital camera with a Canon MP-E 65 mm macro lens (Canon, Tokyo, Japan) and StackShot-Macrorail (Cognisys Inc., MI, USA) The photos were then combined with Helicon Focus 6.8.0. (Helicon Soft, Ukraine), and all photos were improved with Adobe Lightroom classic (Adobe Systems, CA, USA). The antennal and pronotum types and characters follow those proposed by Hulcr et al. (2007) and subsequently elaborated upon by Smith et al. (2020). Length was measured from the pronotal apex to the apex of the declivity, and width was measured at the widest part of the specimen.

Tricosa Cognato, Smith & Beaver, 2020
Type species. Xyleborus metacuneolus Eggers, 1940. Diagnosis. Antennal funicle four-segmented; antennal club with one or two sutures visible on the posterior face; protibia distinctly or obliquely triangular with six or fewer denticles on outer margin and posterior face flattened and unarmed; scutellum small, flush with elytra surface; mycangial tufts absent; elytra attenuate; posterolateral costa absent. Similar genera. Cryptoxyleborus, Cyclorhipidion, and Fraudatrix. Diagnosis. This species is distinguished by its stoutness: 2.35 mm long, 2.40× as long as wide. The combination of the following characters is diagnostic: lateral margin of elytra feebly broadened apically; elytral disc convex; discal striae and interstriae uniseriate punctate; stria weakly impressed and interstriae elevated; anterior margin of pronotum with six moderate serrations.
Description (female). 2.35 mm long, 2.40× as long as wide. Body dark brown, except appendages yellowish brown. Body more robust, less elongate. Head: epistoma entire, transverse, lined with a row of short, hair-like setae. Frons flat from epistoma to middle level of eye, then slightly convex upward to vertex; lower portion of surface at medial line shagreened, subshining; sides of medial line glabrous, strongly shinning; upper portion shagreened, subshining; frons with widely separated, small granules, with each granule decorated with long, fine, hair-like setae. Eyes weakly emarginate above level of antennal insertion; upper portion of eyes slightly smaller than lower part. Submentum slightly impressed below genae, widely triangular at base. Antennal club type 3 (Hulcr et al. 2007;Smith et al. 2020); scape regularly thick, as long as club. Antennal funicle four-segmented; first segment longest and other segments approximately equal in length. Pedicel shorter than funicle. Club flattened, approximately circular (type 3) (Hulcr et al. 2007;Smith et al. 2020); segment 1 corneous, transverse on anterior face, occupying basal ~1/3; segment 2 slightly concave, corneous and corneous line very narrow; segments 1 and 2 present on posterior face.
Male. Unknown. Etymology. L. uniseriata: uni-= one; series = row. Refers to the arrangement of strial and interstrial punctures in one line. A variable adjective.

Discussion
Tricosa uniseriata is the smallest and stoutest Tricosa species. The proportion of this species' body is 2.40× as long as wide as compared to the other species. The elytra are feebly widened 3/4 from the base and slightly tapered to apex as compared to T. hipparion where the elytra are parallel sided 2/3 from the base and tapered to the apex Smith et al. 2022). Its pronotum is less posteriorly elongate, which is similar to T. hipparion and T. mangoensis (Schedl, 1942), and different from the other species, which have a more posteriorly elongated pronotum. The elytral apex is less tapering, broadly rounded, and similar to T. hipparion.

Key to the species of Tricosa (females only)
Modified from Cognato et al. (2020).