Heterochele Viswajyothi and Clark, 2021

Viswajyothi, Keezhpattillam & Clark, Shawn M., 2021, A new genus and two new species of Galerucinae from Costa Rica (Coleoptera: Chrysomelidae), Journal of Natural History 54 (47 - 48), pp. 3103-3119 : 3105-3113

Heterochele Viswajyothi and Clark , gen. nov.

( Figures 1–7 )

Diagnosis

Superficially, this genus resembles small (2.7–3.9 mm long) Diabrotica Chevrolat or Acalymma Barber. However , males can easily be distinguished from either of these genera by the deep impression on the last abdominal ventrite ( Figures 2 (b, (6d))). Females can easily be distinguished by the appendiculate (rather than bifid) tarsal claws.

In the key to genera of Phyllecthrites provided by Moura (2010), males would key to Parabrotica Bechyné and Bechyné (couplet 4), but Heterochele differ from the genus Parabrotica in having the above-mentioned abdominal impression. Moreover, the mesotibial concavity of Heterochele is shallow and rather indistinct ( Figure 1 (c), 4(b), 5(a)). Females would key to couplet 9, at which point the user would be frustrated, since males are needed to proceed further in the key.

Description

Antennal fossae positioned near mid-level of eye. Terminal maxillary palpomere as long as or slightly longer than broad, trianglar, evenly narrowed from base to acute apex. Anterior edge of pronotum lacking bead or fringe of setae; lateral carina of pronotum well developed, with sparse fringe of setae (easily rubbed off and sometimes difficult to see); posterior pronotal edge lacking fringe of setae, with poorly developed bead laterally, without bead mesally. Elytral disc with long, suberect, posteriorly inclined setae ( Figure 4 (a,b)); majority of setae arranged in five or six longitudinal rows, one along epipleural ridge, one near sutural margin, others in between; a few setae scattered outside of rows; basal half of epipleuron narrow, nearly vertical; distal half of epipleuron extremely narrow, nearly attaining elytral apex, obliquely slanted inward in distal half. Procoxae mesally contiguous; procoxal cavities posteriorly open. Mesepimeron and mesepisternum glabrous. Middle tibia of male slightly concave at distal fifth, on side towards femur ( Figure 1 (c), 4(b), 5(a)). Male tarsal claws bifid; female claws appendiculate. Male fifth abdominal ventrite with median depression in posterior half; lateral borders of depression steep, forming acute carina ( Figures 2 (b), Figures 6 (d)). Aedeagus asymmetrical; basal spurs absent.

Type species

Heterochele actias Viswajyothi and Clark , sp. nov.

Etymology

The genus name, Heterochele , is Greek for ‘different claws’. It refers to the sexually dimorphic tarsal claws. The name is a female noun.

Comments

The heterogeneous condition of the tarsal claws (bifid in males, appendiculate in females) is extremely unusual. However, this is not unprecedented among the Galerucinae . For instance, Hyperbrotica Bechyné and Bechyné also has bifid claws in the male (clearly bifid on the front and middle legs, also bifid but with a slightly broader inner lobe on the hind legs). Like Heterochele , female Hyperbrotica have appendiculate claws. Erynephala Blake and most species of Monoxia LeConte have bifid claws in males and simple claws in females.

Tibial spurs were observed on all legs of some of the females of Heterochele . However, they are extremely tiny and difficult to see among the nearby setae. Indeed, they were not seen on some of the other females, although they may have been present. No tibial spurs were detected on any of the males.

Based on the absence of basal spurs on the aedeagus, and on the general appearance, Heterochele is tentatively placed in the subtribe Diabroticina of the tribe Luperini . However, the deep depression on the last male ventrite and the strongly asymmetrical aedeagus are anomalous in the subtribe, but they are similar to the condition in some genera of Galerucini. Even if the genus indeed belongs in Diabroticina , the relationship to other genera of the subtribe is debatable. The general appearance of the beetles, including the suberect elytral setae, suggests a relationship to Acalymma (section Diabroticites). In spite of this, we tentatively place Heterochele in the section Phyllecthrites. The concavity of the male mesotibia, although very shallow, supports this placement. Furthermore, the appendiculate claws of the female are congruent with most Phyllecthrites, but not with Diabroticites. Conversely, bifid claws (present in male Heterochele ) are unusual in Phyllecthrites, although present in a few genera, such as Deinocladus Blake.

Figures

Figure 1. Heterochele actias, male holotype. (a) Dorsal view; (b) lateral view; (c) ventral view.

Figure 2. Heterochele actias. (a) Paratype, anterior view; (b) male paratype, abdominal ventrites; (c) holotype, median lobe of aedeagus, dorsal view; (d) holotype, median lobe of aedeagus, lateral view; (e) holotype, median lobe of aedeagus, distal portion, ventral view.

Figure 3. Heterochele actias, female paratype. (a) Genitalia; (b) bursa copulatrix, with sclerotised pattern and spermatheca attached; (c) tignum; (d) vaginal palpi; (e) spermatheca; (f) last ventrite; (g) last visible tergite.

Figure 4. Heterochele signiferoides, holotype. (a) Dorsal view; (b) ventral view.

Figure 5. Heterochele signiferoides, holotype. (a) Lateral view; (b) anterior view.

Figure 6. Heterochele signiferoides, holotype. (a) Median lobe of aedeagus, dorsal view; (b) median lobe of aedeagus, lateral view; (c) median lobe of aedeagus, distal portion, ventral view; (d) male abdominal ventrites.

Figure 7. Heterochele signiferoides, female paratype. (a) Spermatheca; (b) vaginal palpi; (c) last visible tergite; (d) last ventrite; (e) tignum; (f) bursa copulatrix, with spermatheca attached.