Notaferrum natalensis ( Pic, 1906 ) Gearner & Philips, 2021

Gearner, Olivia M. & Philips, T. Keith, 2021, Notaferrum n. gen. (Coleoptera: Ptinidae): the first known spider beetle associated with weaver ants, Zoosystema 43 (2), pp. 29-36 : 31-34

Notaferrum natalensis ( Pic, 1906) n. comb.

( Figs 1-4 )

Ptinus elegans Péringuey, 1904: 225 .

Ptinus natalensis Pic, 1906: 227 .

MATERIAL EXAMINED. — Holotype. South Africa • 1 ♀; [ Natal ] Isipingo beach; I.1899; SAM type Acc. No .1261 .

ADDITIONAL LABEL DATA. — “Type” (red label); “natalensis”; “ Lectotypus, Ptinus elegans, Péringuey, des J. Borowski ‘98 ( SAMC)”. Abdominal ventrites on a separate card.

OTHER MATERIAL. — South Africa • 1 ♂; Kwazulu-Natal, iSimangaliso Wetland Park [Previously known as Greater St. Lucia Wetland Park], Sodwana Bay campgrounds; 27.54°S, 32.67°E; c. 40 m; 21- 24.X.2014; R. Stals leg.; Vegetation type: FOz Northern Coastal Forest ; SANC • 1 ♀; Natal, Charters Creek, St. Lucia ; 28.12°S, 32.25°E; 14-16.I.1981; R. Oberprieler leg.; from nest of Oecophylla longinoda ; AcP. 8497; SANC .

DIAGNOSIS. — The generic diagnosis together with the white scale setal pattern on the elytra ( Fig. 1 ) should distinguish this taxon, if other species within this genus are discovered in the future.

SPECIES REDESCRIPTION

Body

Color dark brown to black on head, pronotum, and elytra. Body small and elongate. Length 3.4 ± 0.33 mm (n = 3).

Head ( Fig. 2 )

Head covered in punctures, large shallow irregular and contiguous mediolaterally, medially finer, longitudinally elongate; scattered, white small appressed scales; antennae dark brown, antennomeres 1-8 with moderately dense white appressed scales, first antennomere largest, second small as long as wide, remaining antennomeres longer than wide.

Pronotum

Pronotum mostly smooth with very fine alutaceous sculpture, glabrous except anterior ¼ with round and elongate scattered punctures; pair of medial vertical ridges approximately broadly rounded from anterior to posterior dorsal edge, then declivous to base just past middle, short thin yellow setae scattered on top of ridges; three tubercles on each lateral edge, anterior tubercle rounded, middle concave triangular, somewhat ear-shaped, posterior tubercle small, pointed, recumbent clumped orange trichome setae on lateral edge in between and around tubercles; a broadly rounded U-shaped smooth impression; posterior margin of pronotum narrow anterior of scutellum.

Elytra

Elytral surface covered in rows of round to elongate punctures separately longitudinally by half or less their length, puncture rows separated by about 1.5-2.0 times their diameters, 1 st and 2nd rows slightly obliquely oriented, 3rd and 4th less so; humeral angles raised; scutellum triangular, lateral edges below elytral surface; interpuncture rows of small recumbent dull pale orange setae; white scales forming an irregular transverse band at anterior 1/3, extending medially in an irregular longitudinal band from anterior transverse band to posterior 1/3, lateral clump of setae on each elytron at about posterior 1/3, transverse band of setae at apex and sometimes extending anteriorly along suture.

Ventrites

Ventral surface reddish to dark brown, covered in small white appressed scales mostly covering surface; proventrite smooth, mesoventrite with irregularly shaped, glabrous indentation at middle; lateral edge of fourth ventrite and apical edge of fifth ventrite with scattered fine yellowish setae.

Legs

Legs reddish to dark brown, covered in white scales as on ventral surface; 1 st tarsomere longer than wide, others short in length and width, internal surface of tarsomeres covered in fine gold recumbent setae.

Sexual dimorphism

Antennomeres 6-11 in the maledistinctly more elongate compared to those seen in the female. Male genitalia with elongate narrow parameres with a thick median lobe that is about the same length as the parameres.

DISCUSSION

There is little doubt that Notaferrum n. gen. shares close common ancestry especially with Silisoptinus Pic, 1917 (see Bellés 1988, 2009) and more distantly with Eutaphrimorphus Pic, 1898 (see Bellés 1992). All three genera are hypothesized to compose a single monophyletic lineage based on the possession of a very distinct and similarly shaped large medial smooth and flattened U-shaped shallow depression with a broadly rounded posterior border located medially at the base of the pronotum. Further similarity in these three genera is the anteriorly expanded prosternum that covers in part the ventral portion of the head, a feature that may have evolved to help protect mouthparts, most likely from ants. There are additional taxa from the Americas and southeast Asia (e.g. Prosternoptinus Bellés, 1985 , and Sundaptinus Bellés, 1991 ) that also share this feature but based on other characteristics are not closely related (Mynhardt et al. unpublished).

Another similarity between Notaferrum n. gen. and Silisoptinus is the greatly reduced fourth abdominal ventrite (c. ¼ the length of the third). Further is the strong declivity on the third ventrite that slopes dramatically down to the fourth. In contrast, Eutaphrimorphus has a more typical spider beetle abdomen with the fourth reduced (c. half the length of the third) and the ventrites are all in roughly the same plane.

Notable differences of Notaferrum n. gen. with the other two genera is the lack of two short knobs near the pronotal base positioned laterally. They are very pronounced in Eutaphrimorphus while in Silisoptinus they are smaller and of various shapes depending upon the species. Eutaphrimorphus has two additional knobs positioned more centrally as well. These additional projections are also seen in at least one species of Silisoptinus but are much less pronounced and relatively gently rounded.

Both Notaferrum n. gen. and Silisoptinus also exhibit depression(s) on the ventral surface that are lacking in Eutaphrimorphus ; in Notaferrum n. gen., it is located only on the metaventrite near the middle and is similar to at least two other species of Silisoptinus ( Bellés 1988) including one undescribed (Philips unpublished). But the two described species of Silisoptinus also have a single depression on the abdomen while two undescribed (Philips unpublished) have either only a single depression on the metaventrite or both very weakly developed depressions on both the metaventrite and abdomen. Silisoptinus species are known from the eastern side of the African continent ( Zanzibar and Socotra Islands) as well as Ghana (Philips unpublished) while Eutaphrimorphus is known only from South Africa.

Also possibly related to Notaferrum n. gen. is Dignomus Wollaston, 1862 , and the flightless Pseudomezium Pic, 1897 , with the latter representing a flightless Dignomus (Philips unpublished and see Smiley & Philips 2011). These genera together with Silisoptinus and Eutaphrimorphus may form a monophyletic clade or at least with some close common ancestry. Dignomus as currently defined has a diverse set of pronotal modifications ( Bellés 1996; Smith & Philips unpublished) and may not form a monophyletic clade. But the overall similarity of the pronotum having an anterior and posterior lobe laterally and without much lateral projection in both Notaferrum n. gen. and Dignomus (plus Pseudomezium ) is notable.

One other characteristic feature of the new genus is the presence of a transverse posterior pronotal groove of various degrees and shapes. Many other spider beetle taxa also possess a basal groove of various shapes including the African genera Eutaphrimorphus Pic, 1898 , Silisoptinus Pic, 1917 , Eutaphroptinus Borowski, 2009 , Dignomus Wollaston, 1862 , Pseudomezium Pic, 1897 , Dignomorphus Borowksi, 2009 , as well as some species of the non-African Ptinus (e.g. P. espanyoli Bellés, 1997 ), Tropicoptinus Bellés, 1998 , and members of Trymolophus Bellés, 1990 .

DISTRIBUTION

Notaferrum natalensis n. gen., n. comb. is known only from KwaZulu-Natal province in South Africa ( Fig. 4 ). The current range is a little over 300 km in length, and all records are within 30 km of the coast.This distribution is within the Maputuland-Pondoland-Albany hotspot, one of three biodiversity hotspots in South Africa. Maputuland-Pondoland-Albany is notable in particular for its high plant endemism and is the second richest floristic region in South Africa ( Myers et al. 2000). As the distribution of the weaver ant Oecophylla longinoda extends from Southern Africa through Eastern and Western Africa ( Bolton 1995), one might expect the distribution of Notaferrum natalensis n. gen., n. comb. to be much larger.

BIOLOGY

Notaferrum natalensis n. gen., n. comb. is hypothesized to be a myrmecophile, as one individual was collected in a weaver ant nest ( Oecophylla longinoda , Fig. 3B ). There are no other spider beetles known to be associated with Oecophylla ants anywhere in the world. Only one other southern African genus appears to be a true symphile; Diplocotidus Péringuey, 1899 includes three species currently known from South Africa and Namibia ( Bell & Philips 2008). Unlike this new genus, species are wingless and found in arid or semiarid regions and are associated with ground nesting ants. The food type of Notaferrum natalensis n. gen., n. comb. is unclear, but it may feed on nest detritus, as most species of spider beetles feed on accumulated organic matter, particularly dung and detritus.

Figures

FIG. 1. — Dorsal and lateral views of Notaferrum natalensis (Pic, 1906) n. gen., n. comb.: A, type specimen of Ptinus natalensis Pic, 1906; B, specimen from Sodwana Bay Campground showing some of the variability of recumbent white setae on the elytra; C, specimen from Charters Creek, St. Lucia in lateral view showing the distinct blade-like structures on the pronotum; D, male genitalia. Scale bars: A-C, 1 mm; D, 100 μm.

FIG. 2. — Close-up view of head and pronotum of Notaferrum natalensis (Pic, 1906) n. gen., n. comb.: A, dorsal view; B, frontal view. Note the distinct lateral and dorsal trichomes (see arrows).

FIG. 3. — Ventral surface of Notaferrum natalensis (Pic, 1906) n. gen., n. comb. and host ant Oecophylla longinoda Latreille, 1802: A, ventral surface showing the apically expanded prosternal process that extends beyond the procoxae (see arrow), very reduced length of the fourth abdominal ventrite, and the small depression (devoid of setae) on the metaventrite near the posterior margin; B, host ant specimen, Oecophylla longinoda Latreille, 1802, associated with the specimen from St. Lucia, SANC. Scale bar: 2 mm.

FIG. 4. — Distribution of Notaferrum natalensis (Pic, 1906) n. gen., n. comb. based on three known specimens, South Africa, Kwa-Zulu Natal Province.