''Thasus acutangulus'', the Mesquite Bug also referred to as ''Pachylis'' ''acutangula'' is a

leaf-footed bug Coreidae is a large family of predominantly sap-sucking insects in the Hemipteran suborder Heteroptera. The name "Coreidae" derives from the genus '' Coreus'', which derives from the Ancient Greek () meaning bedbug. As a family, the Coreidae ...

. Swedish entomologist Carl Stål described it in 1859.

Description

Female

The head is black laterally with a reddish-brown disk, while the

ocelli A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...

are ringed with black and feature a lateral yellow semicircle. The first antennal segment is deep reddish-brown with black coloration at the base and apex. The second and third antennal segments have a basal half that is orange and an apical half that is black, while the fourth segment is missing in the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

but appears brown-black in other specimens. The

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

is reddish-brown, with a paler callar region, a black collar, and a thin lateral black line that transitions to yellow posteriorly. The posterior edge is yellow. The scutellum is reddish-brown, with yellow lateral edges and an apex. The corium is dark brown with yellow veins, and the membrane is black. Connexival segments 3–7 exhibit a dark reddish-brown color posteriorly and an orange hue anteriorly. The abdominal dorsum is black. The thoracic pleura are broadly reddish-brown, progressively darkening to black near the coxa and posterior edge. Anterior lobe of metathoracic scent gland opening black, bordered by yellow. Legs reddish-brown, apices and bases of segments black; tarsi black. Abdominal sterna reddish-brown, apicolateral borders of each black. Spiracle ringed with black. Structure: Apical of antennal 3 expanded, slightly asymmetrically. Pronotal rise about 60°; lateral edge crenulate; humeral angles acute. Connexivum exposed lateral to wings; connexival segments 3–7 with apicolateral spines, that on 3 very small; that on 7 smaller than that on 6. Note: all other female specimens of ''T. acutangulus'' examined, lack a seventh-connexival spine. Hind tibial expansion without large tooth, anterior margin smooth, posterior margin with small teeth; hind coxae with small protuberance; hind trochanter with small spine. Recognized by its large size, humeral angles exposed, third antennal segment broad, obovate, and foliate, second antennal bicolored, fourth antennal brown to black, and larger (usually above 7.30 mm), and femora and tibiae entirely black or bright orange with anterior and posterior third black and in each case without orange rings. Features which distinguish ''T. acutangulus'' from the related '' T. gigas'' and '' T. neocalifornicus'', are discussed under these species.

Range

Most commonly recorded in Mexico and Guatemala. The species has been recorded in Mexico, specifically in Veracruz (Orizaba and Misantla), as well as in Guatemala (Senahu and Cerro Zunil). In British Honduras (now Belize), it has been documented along the River Sarstoon. A record from Costa Rica (Guanacaste) is likely a misidentification, as noted by Distant (1881–1892), Aldrich and Blum (1978), and Walker (1871). Additionally, reports of this species in the United States are considered misidentifications of '' Thasus neocalifornicus''.

Habitat

The foliage of native trees. Mostly seen occurring from March to August, with a large spike during the months of April and May specifically.

Ecology

Schaefer and Mitchell (1983) noted that the food plant record previously attributed to this species by Aldrich and Blum (1978) is likely misidentified and should instead correspond to '' Pachylis laticornis''.

Taxonomy

The reason ''Thasus acutangulus'' is also referred to as ''Pachylis acutangula'' stems from the historical difficulty in distinguishing these two genera. Both ''Pachylis'' and ''Thasus'' share nearly identical diagnostic characteristics, including robust black bodies, expanded antennomeres, and metatibiae (tibiae of the hind legs). The primary distinction—whether the metatibiae expand

ventrally Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

(''Pachylis'') or on both sides (''Thasus'')—was once used to separate them taxonomically. However, recent

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

studies have found this trait to be homoplasic, meaning it evolved independently and does not reliably differentiate the two genera. As a result, the traditional classification has been re-evaluated, leading to taxonomic uncertainty and the use of both names for the same species in different contexts.

References

{{Taxonbar, from=Q10695235 Nematopodini Insects described in 1859