Acantheremus Karny 1907

1907 Karny, Abh. Zool.-bot. Ges. Wien 4(3): 8; type species: Acantheremus elegans Karny, by original designation

1999 Naskrecki and Otte, Illustr. Cat. Orthop. I (CD

ROM) >>references; types illustrated

Slender to moderately robust; both sexes macropterous. Head with fastigium of vertex strongly produced into sharp cone, 2-3.5 times as long as diameter of eye; apex of fastigium blunt or ending in one or two small spines. Head robust, frons flat or weakly convex; genae with strongly developed lateral carinae, continuous with carinae on fastigium of vertex. Eyes globular, moderately protruding. Ovipositor straight or weakly curved; apex slightly thickened, minutely serrate, distinctly darker than remaining portion of ovipositor.

Description (male except where specified)

Head.— Fastigium of vertex produced into prominent, slender cone, 2 to 3.5 times as long as diameter of eye; dorsal surface of fastigium smooth or tuberculate; fastigium with well developed lateral carinae; lateral ocelli situated at bases of carinae; apex of fastigium blunt, or with one or two small apical spines; basal portion of fastigium of vertex with a prominent knob ventrally, well separated from fastigium of frons.Antennal sockets separated by distance equal to 0.6-1.0 diameter of eye. Eyes globose, moderately projecting; genae smooth or with two parallel rows of small tubercles. Frons flat or weakly convex; genae with strongly developed lateral carinae, continuous with those on fastigium of vertex.

Thorax and wings.— Dorsal surface of pronotum smooth or finely tuberculate, flat; anterior margin of pronotum straight, posterior margin straight or weakly convex; lateral lobes with posterior angle rounded or acute. Thoracic auditory spiracle large, elliptical, completely hidden under lateral lobes of pronotum. Prosternum unarmed, mesosternum unarmed or with a pair of small, widely separated, vertical spine-like lobes; metasternum unarmed.

Wings in both sexes fully developed, surpassing apices of hind femora. Stridulatory apparatus of male well developed; stridulatory file straight or weakly curved, with very high number (124-585) of narrow, lamelliform, very closely spaced teeth; stridulatory area of left wing covered with archedictyon or almost devoid of secondary venation; mirror of right wing about as long as wide, with or without veinlet parallel to AA1. Posterior margin of front wing straight or weakly concave; apex of front wing narrowly rounded.

Legs.— Fore coxa with an elongate, sometimes laterally flattened, forward projecting spine dorsally; middle and hind coxa without spine; all trochanters unarmed. Fore femur dorsally unarmed, anterior (inner) margin of femur with 4-5 spines; middle femur unarmed dorsally, anterior (outer) margin of femur with 4-5 spines; hind femur unarmed dorsally, anterior (outer) ventral margin armed with 7-11 spines, inner margin unarmed; genicular lobes of all femora armed with long spines, outer (anterior) spine usually slightly longer than inner (posterior) one. Front tibia unarmed dorsally, both ventral margins with short, immovable spines; tympanum on fore tibia bilaterally closed, tympanal slits facing forward, tympanal area moderately swollen; middle tibia unarmed dorsally or with 3-4 dorsal spines, ventrally armed on both margins; hind tibia armed on all four dorsal and ventral margins; apex of tibia with two pairs of ventral and one pair of dorsal movable spurs.

Abdomen.— Dorsal surface of abdominal terga smooth, unmodified. Male 10th tergite with surface smooth, its posterior margin weakly to distinctly emarginated; supraanal plate in both sexes small, broadly rounded apically; male cercus variable, either short and robust, with or without apical spine, and with a large inner spine, or laterally flattened, unarmed; paraprocts unmodified; female cercus, simple, narrowly conical. Subgenital plate of male variable, either broadly triangular, with a very shallow apical emargination, or almost parallel-sided, with very deep apical incision; styli short, 1.5-2.0 times as long as thick; female subgenital plate either triangular, with triangular apical incision, or with two widely divergent, upcurved lobes. Male internal genitalia with weakly sclerotized inner margins of phallic lobes but without well developed titillators. Ovipositor narrow, its margins parallel, straight or slightly curved upwards; both dorsal and ventral margins of ovipositor smooth; apex of ovipositor slightly but noticeably thickened laterally, darker than remaining part of ovipositor and slightly serrated on both upper and lower valvulae. Length of ovipositor from 0.6 to approximately 1.6 times length of hind femur.

Coloration.— General coloration green; frons green, clypeus and labrum sometimes yellow; scapus, lateral carinae of fastigium of vertex and genae yellow, sometimes with red edges; thorax and abdomen green or yellowish; legs green, femoral spines often yellow or pink; tegmina green with hind margins sometimes with narrow red and yellow edge, sometimes tegmina with widely scattered dark dots, hind wings transparent. Dried specimens in entomological collections usually turn yellow with time.

Remarks.— The genus, which includes 9 described species was recently revised by Naskrecki (1997).

Acantheremus species range from southern Central America (Costa Rica, Panama), to the Caribbean (Dominica) and to South America (Colombia, Surinam, Guyana, Venezuela, Brazil, Peru).

Unlike members of the closely related Copiphora, which inhabit primarily the understory vegetation or even the ground level of the forest, species of Acantheremus seem to be restricted to the canopy level and never descend to the ground. This, combined with the apparent rarity of these insects, makes field observations extremely difficult and few conclusions can be drawn about the biology of Acantheremus.

Modifications of the apical part of the ovipositor suggest that females of all Acantheremus spp. deposit eggs in plant tissues, rather than in the ground, where at least some members of the genus Copiphora oviposit. The minutely toothed edges of the apical portions of both upper and lower valvulae suggest that females make incisions in plant tissues. A female of A. colwelli was seen depositing eggs in a stem of an unidentified vine. This species was also collected from the following tree species: Virola koschnyi Warb. (Myristicaceae), Dendropanax arboreus (L.) Decne. and Planch. (Araliaceae) and Pentaclethra macroloba (Gavilán) (Mimosaceae).

Probably all species of Acantheremus are predominantly predaceous. In captivity, nymphs of A. colwelli readily accepted both live and dead insects and rather reluctantly consumed plant material. Live insects, such as nymphs of other katydids and small moths, were swiftly captured with the fore legs and crushed with the powerful mandibles typical of the genus. Gut content analysis of other species revealed numerous cuticular elements of insect bodies, such as parts of mandibles and compound eyes of beetles and wing scales of Lepidoptera.

Little is known about the acoustic behavior of Acantheremus spp., and only A. colwelli has been recorded (see below for the song description).