Chaska, Darby, Michael, 2016

Darby, Michael, 2016, Studies of Peruvian Ptiliidae (Coleoptera) 5: Chaska nawi, a new genus and species of Acrotrichinae, Acrotrichini, Zootaxa 4161 (1), pp. 133-136 : 133-134

Chaska gen. n. ( Acrotrichinae , Acrotrichini)

Type species Chaska nawi . sp. n. (gender feminine).

Description. Body elongate, rounded, dorsal surface including the head pubescent the setae arising from shallow depressions. Antennae with 11 segments, 1 -2 forming the scape and pedical being larger than 3-11, and 9-11 forming a tapering club, all segments bearing long setae and antennomere 10 additional sensillae ( Fig. 2 ). Mentum with two long setae arising posterior to the smaller medial setae ( Fig. 11 ). Sides of pronotum with a narrow raised margin, hind angles rounded and produced backwards ( Fig. 8 ). Elytra rounded apically exposing +/- 3 abdominal segments, sides with epipleura and a raised border widening towards the humeri which terminate in a small tooth (visible in ventral view) ( Fig. 9 ). Wings of usual featherwing type. Proventrum in front of procoxae with a band of setae ( Fig. 5 ). Mesoventral collar not extending onto the humeri, with a narrowly bordered anterior margin and a crenulated posterior margin ( Fig. 7 ); mesoventrum with a small medial, pointed oval stub behind the collar and a raised keel extending posteriorly to 2/3 distance between the mesocoxae ( Fig. 6 ). Mesofemora with a long row of stout setae on the posterior margin ( Fig. 11 ). Metaventrum pubescent, posterior margin between the metacoxae with a convex margin and sharp lateral points ( Fig. 6 ). Metacoxae with small rounded plates tapering to the lateral margins ( Fig. 6 ). Metafemora with a row of ventrally projected short stout setae ( Fig. 13 ). Pygidium composed of tergites IX and X fused seamlessly together and with a medial and two lateral teeth ( Fig. 15 ). Male ventrite VI with a shallow curved excision, ventrite VII small covering the excision in ventrite VI and with an anteriorly directed apodeme ( Fig. 14 ).

Diagnosis. Superficially similar to the more rounded species of Acrotrichis Motschulsky and likely to be confused with that genus if the dorsal characters alone are examined. The most important distinguishing features are: the mesoventral collar which does not extend onto the humeri and possesses a crenulated posterior margin unique in the Acrotrichinine species described to date, the rounded pronotal hind angles, the raised and slightly sinuate elytral borders with a small humeral tooth, the position of the two long setae on the mentum and the convexly rounded posterior margin of the metaventrum between the metacoxae (in Acrotrichis straight or concave). In addition the aedeagus lacks the hooks prominent in many species of Acrotrichis .

Remarks. The mesoventral collar not extending onto the humeri is also a feature of one other Acrotrichinine with backwardly pointing pronotal hind angles Phytotelmatrichis Darby and Chaboo , but the members of that genus may be distinguished from Chaska by their proximate metacoxae, and their flatter and more posteriorly tapering shape.

Figures

FIGURES 1 – 10. Chaska nawi n. sp. 1. Habitus. 2. Antennomeres 8 - 11. showing arrangement of setae, and presence of sensillae on antennomere 10. 3. Aedeagus ventral view. 4 Aedeagus side view. 5. Underside of head and proventrum showing band of setae anterior to procoxae x 430. 6. Meso- and metaventra x 415. 7. Mesoventral collar showing crenulated posterior margin x 1040. 8. Pronotum showing rounded posterior angle, laterodorsal view x 1520. 9. Elytral epipleuron showing small humeral hook x 580. 10. Mentum and submentum showing chaetotaxy.

FIGURES 11 – 15. Chaska nawi n. sp. 11. Profemora and tarsus showing arrangement of setae, ventral view x 970. 12. Terminal abdominal ventrites x 410. 13. Metafemora and tarsus showing tarsal claws and arrangement of setae, ventral view x 1540. 14. Male ventrites VI & VII. 15. Male pygidium, dorsal view.