Acrotrichis Motschulsky, 1848

Darby, Michael, 2019, New Ptiliidae (Coleoptera) from Sarawak in the spirit collection of the Natural History Museum, London, European Journal of Taxonomy 512, pp. 1-50 : 29-30

Genus Acrotrichis Motschulsky, 1848

The largest ptiliid genus, distributed worldwide, with numerous described species. Unless stated otherwise, all species share the following features: body elongate, usually rather broad, relatively flat, dorsal surface including the head pubescent. Antennae with 11 antennomeres I–II forming the scape and pedicel being much larger than III–XI, and IX–XI forming a loosely formed and tapering club; all antennomeres bearing long setae. Sides of pronotum with a narrow raised margin, and hind angles produced backwards. Scutellum without distinguishing features. Metascutellum with a single lateral spine or spur on each side (not present in any other Ptiliidae subfamily ( Hall 2000). Elytra truncate apically exposing ± four abdominal segments. Proventrum narrow in front of the procoxae. Mesoventrum with a well-developed collar extending across the pleura and a raised keel between the mesocoxae. Metasternum pubescent, posterior margin between the metacoxae with sharp lateral points. Metacoxae with rounded plates tapering towards the lateral margins. Abdominal tergites II–V with wing folding spicule patches. Pygidium composed of tergites IX and X fused seamlessly together with or without ¾ teeth. Abdominal ventrite I without femoral lines. Male ventrite VI with a more or less curved excision, ventrite VII small, covering the excision in ventrite VI, and with an anteriorly directed apodeme. Aedeagus symmetrical in dorsal/ventral view often, but not always, with two hooks. Spermatheca well developed. Wings of usual featherwing type. Parthenogenetic species have been recorded.

Several attempts have been made to establish subgenera and, more recently, species groups within specific geographic faunas. However, the validity of some of these classifications is questionable if a more holistic view is taken and allowance made for new criteria resulting both from the discovery of many new species and also from better descriptions of old ones. For this reason and until the genus is better understood, no attempt is made here to assign species to particular groups and they are treated instead in one alphabetic sequence. Further information together with a more detailed account of the morphological features useful in separating species of Acrotrichis is included in Darby (2014a).

Key to the Sarawak species of Acrotrichis and Storicricha

1. Metaventral extension between metacoxae bifid the two spines united ( Fig. 23H ) ......................... 2

– Spines on metaventral extension not united (though gap in A. bidens sp. nov. is short) .................. 3

2. Female spermathecal pump fan shaped ( Fig. 24D ) .............................. Storicricha umbella sp. nov.

– Female spermathecal pump flat topped, duct linear ............................ Storicricha resticula sp. nov.

3. Elytral cells microtrichiate ( Fig. 17D ) ................................................. A. cognata (Matthews, 1877)

– Elytral cells without microtrichae ..................................................................................................... 4

4. Submentum with> 15 outstanding setae ( Fig. 17F ) ............................................. A. bubalis sp. nov.

– Submentum with <12 setae, not so outstanding .............................................................................. 5

5. Insect of globose form, elytra with wide epipleura ( Fig. 19F ) ............................. A. globosa sp. nov.

– Insect more elongate, elytral epipleura if present much shorter and narrower ................................. 6

6. Pronotal lateral margins sinuate, hind angles clearly acute ( Figs 14B , 20B ) ................................... 7

– Pronotal angles not clearly acute ...................................................................................................... 8

7. Large species,> 0.85 mm, pronotal sinuation less pronounced .............................. A. acuta sp. nov.

– Smaller species <0.85 mm ................................................................................... A. hanskii sp. nov.

8. Male with a long row of setae on ventrite VI ( Fig. 17G ) ...................... A. cursitans (Nietner, 1856)

– Male genitalia without a long row of setae on ventrite VI ............................................................... 9

9. Separation of metacoxae very short ( Fig.16H ) ....................................................... A. bidens sp. nov.

– Separation of metacoxae wider ....................................................................................................... 10

10. Large species> 0.95 mm, aedeagus ( Fig. 17C ) ............................................ A. agricola Darby, 2019

– Smaller species <0.90 mm ..............................................................................................................11

11. Larger species> 0.70 mm ............................................................................................................... 12

– Smaller species <0.70 mm ............................................................................................................. 13

12. Metacoxae widely separated ( Fig. 22G ) .................................................................. A. plaga sp. nov.

– Separation of metacoxae shorter ............................................................................. A. geiseri sp. nov.

13. Pronotal angles broad and flattened ( Fig. 15B ) ......................................................... A. belli sp. nov.

– Pronotal angles not broad and flattened .......................................................................................... 14

14. Female spermatheca without a long coiled duct ( Fig. 17E ) ....................... A. britteni Johnson, 1969

– Female spermatheca with a long coiled duct ( Fig. 21E ) .................................. A. muluensis sp. nov.

Figures

Fig. 23. Storicricha resticula sp. nov. A. Habitus. B. Hind angle of pronotum viewed at 45°. C. Antennomeres III–XI. D. Spermatheca. E. Aedeagus. F. Mentum and submentum ×1000. G. Meso- and metaventra ×320. H. Bifid process between metacoxae ×1700. I. Pygidium.

Fig. 24. Storicricha umbella sp. nov. A. Habitus. B. Hind angle of pronotum viewed at 45°. C. Antennomeres III–XI. D. Spermatheca. E. Aedeagus. F. Meso- and metaventra ×340. G. Mentum and submentum ×1300. H. Abdominal ventrites.

Fig. 17. A. Acrotrichus britteni Johnson, 1969, spermatheca. B. Acrotrichis cursitans Nietner, 1856, setae on ventrite VI ×1420. C. Acrotrichis agricola Darby, 2019, spermatheca. D. Acrotrichis cognata (Matthews, 1877), microtrichae on elytra ×1520. E. Baeocrara sp., medial portion of collar ×3150. F. Acrotrichis bubalis Darby, 2019, setae on submentum ×1320.

Fig. 19. Acrotrichis globosa sp. nov. A. Habitus. B. Hind angle of pronotum viewed at 45°. C. Antennomeres III–XI. D. Spermatheca. E. Aedeagus. F. Meso- and metaventra ×280. G. Mentum and submentum ×800. H. Pygidium.

Fig. 14. Acrotrichis acuta sp. nov. A. Habitus. B. Hind angle of pronotum viewed at 45°. C.Antennomeres III–XI. Da–Db. Spermatheca. E. Aedeagus. F. Meso- and metaventra ×325. G. Pygidium. H. Mentum and submentum ×820.

Fig. 20. Acrotrichis hanskii sp. nov. A. Habitus. B. Hind angle of pronotum viewed at 45°. C. Antennomeres III–XI. D. Spermatheca. E. Aedeagus. F. Meso- and metaventra ×425. G. Mentum and submentum ×1600. H. Pygidium.

Fig. 16. Acrotrichis bidenssp. nov. A. Habitus. B. Hindangle of pronotum viewed at 45°. C.Antennomeres III–XI. D. Aedeagus. E. Spermatheca. F. Mentum and submentum. G. Meso- and metaventra. H. Bifid process of the metaventrum between the metacoxae. I. Pygidium

Fig. 22. Acrotrichis plaga sp. nov. A. Habitus. B. Spermatheca. C.Aedeagus. D. Mentum and submentum ×1580. E. Hind angle of pronotum viewed at 45°. F. Antennomeres III–XI. G. Meso- and metaventra ×272. H. Pygidium.

Fig. 15. Acrotrichis belli sp. nov. A. Habitus. B. Hind angle of pronotum ×1460. C. Antennomeres III–XI. D. Spermatheca. E. Aedeagus. F. Meso- and metaventra ×420. G. Pygidium. H. Mentum and submentum ×1500.

Fig. 21. Acrotrichis muluensis sp. nov. A. Habitus. B. Hind angle of pronotum viewed at 45°. C. Antennomeres III–XI. D. Aedeagus. E. Spermatheca. F. Mentum and submentum ×1120. G. Meso- and metaventra ×305. H. Pygidium.