Anthrenus, Geoffroy, 1762, Geoffroy, 1762

Holloway, Graham J., Herrmann, Andreas & Querner, Pascal, 2025, Redescriptions of the European Anthrenus Geoffroy, 1762 belonging to the subgenus Helocerus Mulsant & Rey, 1868 (Coleoptera, Dermestidae, Megatominae), Arquivos Entomolóxicos 32, pp. 89-97 : 91-95

Results

Fig. 1 shows the aedeagi of the three study species. Anthrenus (H.) minutus aedeagus ( Fig. 1b ) is distinctive with straight, slim parameres, thickened along their outer edges, and carrying long spikey setae along the inner margin from the paramere tip spreading into the paramere disc. It is easy to differentiate A. (H.) minutus aedeagus from the other two species, so there is no reason to examine its aedeagus further. Anthrenus (H.) fuscus ( Fig. 1a ) and A. (H.) polonicus ( Fig. 1c ) are very similar in dorsal aspect. Anthrenus (H.) fuscus parameres carry long setae along the inner margin from the tip and spreading across the paramere disc at about halfway. Anthrenus (H.) polonicus has straight spikey setae from the tip that run down the inner margin and follow a straight line into the paramere disc, stopping AT ABouT hAlfWAY. MroczkoWSki’S (1951) illuSTrATion of A. (H.) polonicus aedeagus is very accurate, including the setal distribution but his illustration of A. (H.) fuscus aedeagus deviates slightly from Fig. 1a . Mroczkowski (1951) suggests that A. (H.) fuscus paramere tips are shorter, blunt and tilt in towards each other. That is not evident in Fig. 1a .

Mroczkowski (1951) illustrated the aedeagi of A. (H.) fuscus and A. (H.) polonicus in lateral aspect to further confirm species validity, shown here in Fig. 2 . Anthrenus (H.) fuscus parameres ( Fig. 2a ) are concave along the ventral (upper side in Fig. 2 ) margin, sweeping very slightly upwards, ending in blunt, rounded tips (NB the parameres could also appear to sweep upwards slightly if they curved in towards each other as proposed by Mroczkowski, 1951). Anthrenus (H.) polonicus parameres ( Fig. 2b ) are not concave along the ventral or the dorsal margins which terminate at a sharper tip pointing directly posterior. The median lobes are visible through the parameres. The main difference is that there is a knob (indicated) or angle on the ventral surface of A. (H.) polonicus median lobe at the point where the lobe bifurcates (see Fig. 1 ). This species-specific feature was noted and illustrated by Mroczkowski (1951). No such knob or angle can be seen on A. (H.) fuscus median lobe.

The other internal character that is often useful when differentiating among species or describing new species is sternite IX ( Fig. 3 ). Sternite IX in the three Helocerus species studied here is a very thin, fragile sheet. All three are pale brown across the central component and down to the anterior attachment point. Around the brown component is a whitish edge to the lateral margin from about halfway, up around the posterior margin and down the other lateral margin. The whiter tissue indicates less sclerotinisation. In A. (H.) fuscus ( Fig. 3a ) the white zone is broad and carries many straight setae along both lateral zones up to and including the outer corners of the posterior margin. The centre of the evenly rounded posterior margin is devoid of long setae but perhaps carries numerous small setae. Anthrenus (H.) minutus sternite IX ( Fig. 3b ) is again distinctive. The white edging is not as wide and obvious as A. (H.) fuscus but the setae emerging from the white tissue are very stout and thick, and less numerous than A. (H.) fuscus . The posterior margin is flat rather than rounded and the centre of the posterior margin carries no thick bristles but perhaps has a row of finer bristles. Anthrenus (H.) polonicus sternite IX ( Fig. 3c ) has a rounder profile than both A. (H.) fuscus and A. (H.) minutus and the browner tissue extends almost to the posterior margin. The bristles are longer, finer, and many are curved. There are more bristles along the posterior margin.

Fig. 4 shows A. (H.) minutus , a male ( Figs. 4a and 4b ) and a female ( Figs. 4c and 4d ). The basal sections of the elytra and the pronotal disc have been rubbed in the male ( Fig. 4a ) but, despite that, it is clear that both the male and the female ( Fig. 4c ) carry many pale-yellow scales on the elytra. Three bands of pale scales are present, basal, pre- and sub-medial but all are so broad that between them they cover most of the elytral surface. In addition to the bands there is an apical mass of yellow scales. The yellow scales are set in a background of brown scales. The pronotum is likewise covered in many pale scales, whitish at the pronotal posterior angles and mostly yellow elsewhere. The male antenna ( Fig. 4b ) is 5 five-segmented, the two basal segments are large and rounded, the 3 rd and 4 th segments are narrower, transverse oblongs; all four of these segments are yellow. The terminal segment is very long, slim, dark brown and hirsute, the lateral margins diverging very slightly to a rounded terminal margin. The female has a six-segmented antenna ( Fig. 4d ), the first five yellow and segments 3-5 squarer than male 3 and 4 segments. Segment 6 forms a more accentuated, shorted club than the male, but again it is dark brown and hirsute.

Fig. 5 shows the colour patterning and antennae of A. (H.) fuscus . Within sex there is some colour variation, although males ( Figs. 5a and 5b ) are darker than females ( Figs. 5d and 5e ). As with A. (H.) minutus , there are three bands of pale scales crossing an otherwise dark background of dark brown scales. However, the two A. (H.) minutus specimens were much paler than all A. (H.) fuscus and if this is consistent across all A. (H.) minutus , differentiating between the two species on the Iberian Peninsula should be straight forward. In addition, and as Erichson (1845) pointed out, the antennal clubs of A. (H.) minutus are dark contrasting with the first four segments whereas A. (H.) fuscus antennae ( Figs. 5c and 5f ) are all red.

The posterior pronotal corners are covered in a patch of bright, mostly white, scales that form a transverse oblong. This oblong is tightest in males ( Figs. 5a and 5b ) whereas yellow scales bleed forward and inwards from the white oblong in females ( Figs. 5d and 5e ). The area between the oblongs and up onto the pronotal disc is largely devoid of scales, especially in male whereas there are a few yellow scales scattered across the area in females.

Fig. 6 shows a range of A. (H.) polonicus habiti along with male and female antennae. Both males ( Figs. 6a and 6b ) and females ( Figs. 6d and 6e ) display a range of patterning depending on the density and number of yellow scales on the background of brown scales. In all cases three bands are evident: sub-basal, sub-medial and pre-apical. Between the bands (and above sub-basal) there is a scattering of yellow scales. Within the bands, A. (H.) polonicus has more white scales mixed in with the yellow scales than A. (H.) fuscus .

In most cases there are many yellow and white scales on the pronotum, focussed on and spreading forward from the pronotal hind angles. There are yellow and white scales all along the posterior pronotal margin. Even in specimens with reduced pale scales on the pronotum there is a pale spot four or five scales width in the centre of the posterior margin above the scutellum. Anthrenus (H.) polonicus does not display clear oblongs of white scales at the hind pronotal angles (cf. A. (H.) fuscus ).

The five-segmented male antenna ( Fig. 6c ) has four yellow basal segments, the first two being larger and rounder than the squarish 3 rd and 4 th segments. The 5 th (terminal) segment is brown, long and hirsute. The anterior margin is flat, the posterior margin diverges from the anterior margin before sweeping inwards to form a rounded tip. Overall, the male antenna appears broader than A. (H.) fuscus ( Fig. 5c ). The female antenna ( Fig. 6f ) is at least six segmented, perhaps even seven. As with the male, the first two segments are (dark) yellow and rounded. The third to the fifth (sixth) are oblong, longer than wide, and dark yellow. The terminal segment is extended, about the length of the other segments added together, so much shorter than the male. No female A. (H.) fuscus in the study sample had more than 5 antennal segments ( Fig. 5f ).

Figures

Fig. 1.- Aedeagi dorsal aspect. 1a.- Anthrenus (H.) fuscus. 1b.- Anthrenus (H.) minutus. 1c.- Anthrenus (H.) polonicus. Scale bars = 100 µm.

Fig. 2.- Aedeagi lateral aspect. 2a.- Anthrenus (H.) fuscus. 2b.- Anthrenus (H.) polonicus, with diagnostic knob on ventral side of median lobe indicated. Scale bars = 100 µm.

Fig. 3.- Sternite IX. 3a.- Anthrenus (H.) fuscus. 3b.- Anthrenus (H.) minutus. 3c.- Anthrenus (H.) polonicus. Scale bars = 100 µm.

Fig. 4.- Anthrenus (H.) minutus. Male: 4a.- Habitus. 4b.- Antenna. Female: 4c.- Habitus. 4d.- Antenna. Scale bars: habiti = 1 mm; antennae = 100 µm.

Fig. 5.- Anthrenus (H.) fuscus. Male: 5a.- Habitus. 5b.- Habitus. 5c.- Antenna. Female: 5d.- Habitus. 5e.- Habitus. 5f.- Antenna. Scale bars: habiti = 1 mm; antennae = 100 µm.

Fig. 6.- Anthrenus (H.) polonicus. Male: 6a.- Habitus. 6b.- Habitus. 6c.- Antenna. Female: 6d.- Habitus. 6e.- Habitus. 6f.- Antenna. Scale bars: habiti = 1 mm; antennae = 100 µm.