Globicornis peckhamae, Holloway & Luna, 2023

Holloway, Graham J. & Luna, Ivan Cañada, 2023, Globicornis peckhamae (Coleoptera, Dermestidae, Megatominae), a new species from Mallorca, and a description of Globicornis bifasciata, Zootaxa 5306 (2), pp. 297-300 : 298-300

Globicornis peckhamae sp. nov.

( Figures 1–2 )

Specimen examined. Holotype: Globicornis peckhamae sp. nov. Mallorca, Bunyola (39.696N, 2.700E) 4 June 2021 I. Cañada Luna leg. Holotype male NHML . Paratypes 7 males collected same time and place as holotype.

External characteristics. Holotype description: slim, BL = 2.45 m, BW/BL = 0.66. Head with one median ocellus on vertex. Pronotum black and approximately twice as wide as long (PL/PW = 0.57). Elytra brown, noticeably paler than pronotum ( Figure 1A ). Prominent humeri, elytral margins constricting slightly post-humeri continuing almost parallel to each other before sweeping inwards to elytral tips. Pronotum almost as wide as humeri. Posterior margin of pronotum bisinuate. Mid-point of pronotum on posterior margin is a rounded tip above a black, triangular scutellum. From a posterior corner of the pronotum, the lateral margin forms a smooth curve up towards the back of the head and then down to meet the other posterior corner. Body covered in punctures. Some whitish hairs across the base of both elytra. Pale hairs on pronotum interrupted by black, hairless stripe down and across pronotum forming a black cross. Pale hairs across vertex of head. Two fasciae cross elytra consisting of whitish hairs. The sub-basal fascia begins at each humerus, sweeps down across each elytron reaching the suture, and then up towards the scutellum. The pale hairs of the sub-apical fascia start at the lateral margin or each elytron, gently angling down to meet at the elytral suture.

The 10-segmented antenna ( Figure 1B ) carries a large, asymmetrical club (example shown = 323 µm long) consisting largely of antennomere 10. Antennomeres 1 and 2 dark brown and spherical. Antennomeres 3 – 7 a dark yellowish colour, and antennomeres 8–10 dark brown to black. Antennomeres 8 and 9 disk-shaped with antennomere 8 larger than antennomere 7, and antennomere 9 larger than antennomere 8. Antennomere 10 is large and triangular, with a straight ventral margin and a curved dorsal margin. Antennomeres 8 and 9 sit within a large excavation at the base of antennomere 10. Antennomere 10 is covered in short, stiff, regularly distributed setae. Tibiae and femora dark reddish brown, tarsi pale reddish brown. The ventrites are dark brown to black and covered in pale hairs ( Figure 1C ).

Internal characteristics. The aedeagus ( Figure 2A ) is small (example shown = 235 µm). The parameres diverge evenly from the base such that the overall appearance of the aedeagus is not very angular. The parameres are pale brown indicating limited sclerotinization, except for the apical 25% of the parameres which curve in towards the median lobe ending in rounded tips and are soft and entirely transparent. The parameres are deeper dorso-ventrally than they are wide. The inner surfaces of the parameres carry spikey, backward pointing setae ( Figure 2B ). Setae also cover all unsclerotinized surfaces of the parameres.

The median lobe ( Figure 2A ) is broad, consisting of a brown ridge along both sides of the median lobe with paler tissue between the ridges. The ridges are straight and converge only slightly towards the tip of the median lobe. Median lobe is heavily curved dorsally, terminating in a hooked cap ( Figure 2b ). The tip of the median lobe protrudes beyond the dorsal surface of the parameres.

Sternite IX ( Figure 2C , example shown 320 µm long) has a single, broad anterior stem. From the tip of the anterior stem, the lateral margins sweep smoothly outwards to blunt corners before continuing, converging slightly to a broad, rounded posterior tip. The posterior end is adorned with stout black setae that lean inwards towards the midline, but few of these setae protrude beyond the posterior margin. The outer margins of sternite IX carry very few small setae. Beyond the posterior tip, virtually no setae on the dorsal and ventral surfaces.

Confusion species. The only confusion species to consider is G. bifasciata ( Figure 3A ). Externally, G. bifasciata and G. peckhamae are very similar except that in G. bifasciata there is barely any difference in colour between the pronotum and the elytra, both being very dark. Internally, G. bifasciata and G. peckhamae do vary. Globicornis bifasciata aedeagus ( Figure 3B ) is more angular because the parameres diverge strongly from the base before bending sharply towards posterior. The parameres continue almost parallel to each other before folding inwards towards the median lobe. In many G. bifasciata , the paramere tips when dry fold inwards and ventrally ( Figure 3C ). Overall, the aedeagus of G. bifasciata is more sclerotinized and robust than G. peckhamae . This difference is most prominent at the paramere tips of G. bifasciata which are brown rather than translucent. As in G. peckhamae , the median lobe of G. bifasciata consists of heavily sclerotinized outer ridges sandwiching paler tissue, but these ridges converge more strongly in G. bifasciata coming together to form a very narrow tip that is deeper dorsoventrally than it is laterally. The median lobe is more heavily curved than in G. peckhamae which protrudes further beyond the dorsal margins of the parameres ( Figure 3c ). The median lobe terminates in a hooked cap that is narrower than in G. peckhamae . The anterior stem of sternite IX ( Figure 3D ) is narrower than G. peckhamae . The margins sweeps outwards from the anterior stem to sharp angles before turning towards a broad, rounded posterior margin. The posterior margin is adorned with stout, inward pointing setae which extend beyond the posterior margin, unlike G. peckhamae . There are only a few small setae down the lateral margins of sternite IX and nothing beyond about 1/3 from the posterior tip.

Morphometrics. A sample of 16 males were dissected, including G. bifasciata holotype: 8 G. bifasciata and 8 G. peckhamae . The dimensions of the pronota of the two species were almost identical such that mean PL/PW was 0.57 ± 0.12 in both cases. Mean EL of G. bifasciata was 1.66 ± 0.15 (standard deviation) mm and mean EL of G. peckhamae was 1.70 ± 0.12 mm, but G. peckhamae was broader than G. bifasciata with BW/EL = 0.645 ± 0.005 and 0.593 ± 0.007, respectively. BW/EL differed significantly between the two species (t 14 = 6.72, p<0.001).

Discussion. Eight G. peckhamae from a sample of 16 indicates that G. peckhamae is not scarce. Háva (2023) suggests that G. bifasciata can be found in France, Mallorca, Monaco, Sardinia, Sicilia, Spain, Algeria, and Tunisia. The present study casts doubt on the accuracy of this distribution due to the similarity of the external characteristics of the two species. All that is now known for certain is that both species can be found on Mallorca and G. bifasciata can be found in France, presumably southern France ( Perris 1866). More work needs to be done to establish the true distributions of the two species, both the habitat related distribution in Mallorca and more widely across western Mediterranean. If these data can only be gathered via dissection, progress will be slow. However, a statistically significant difference in the body width of the two species was indicated here. Of course, a statistically significant result might not equate with a usable result if there is a great deal of overlap between the two species. From the relatively small samples examined here, an overlap around BW/EL = 0.625 was indicated. A study involving larger sample sizes needs to be carried out to establish exactly where the overlap lies, and which BW/EL values definitively indicate one species or the other. In addition, a clear colour difference between the pronotum and the elytra was noted for G. peckhamae which is not present, or at least not obvious, in G. bifasciata . If the presence or absence of this colour difference is consistent, in conjunction with the morphometric differences it might be possible to differentiate between G. bifasciata and G. peckhamae with confidence without the need to resort to dissection.

Etymology. The species is named after Katie Peckham who discovered the species whilst working towards an MSc by Research in Entomology.

Figures

FIGURE 1. Globicornis peckhamae sp. nov. holotype, A: habitus (scale bar = 1mm), B: antenna (scale bar = 100µm), C: ventrites (scale bar = 1mm).

FIGURE 2. Globicornis peckhamae sp. nov. holotype, A: aedeagus ventral aspect, B: aedeagus dorso-lateral aspect, C: sternite IX. Scale bars = 100µm in all cases.

FIGURE 3. Globicornis bifasciata, A: habitus holotype (scale bar = 1mm), B: aedeagus holotype ventral aspect (scale bar = 100µm), C: aedeagus lateral aspect (scale bar = 100µm), D: sternite IX (scale bar = 100µm).