Axinotarsus pulicarius

Hoebeke, Richard & Wheeler, Alfred G., 2012, Axinotarsus pulicarius (F.) (Coleoptera: Melyridae: Malachiinae), a soft-winged flower beetle new to North America, Zootaxa 3482, pp. 82-87 : 83-85

Axinotarsus pulicarius (F.)

( Figs. 1–4 )

Malachius pulicarius Fabricius, 1775: 308 .

Cantharis leucogastra Preyssler, 1790: 58 .

Cantharis nemoralis Gmelin, 1790: 1898 .

Malachius pulicarius var. truncatellus Fallén, 1807: 25 . Axinotarsus pulicarius var. martialis Pic, 1918: 17 . Axinotarsus pulicarius var. obscuratus Escalera, 1926: 244 .

Systematics. Axinotarsus Motschulsky is an exclusively Old World genus of soft-winged flower beetles comprising 34 species distributed throughout the Palearctic Region (Europe, North Africa, and Asia) ( Mayor 2007). Three subgenera are recognized, with the majority of species (29), including A. pulicarius , placed in the nominate subgenus Axinotarsus . As in the majority of malachiine melyrids, adults of Axinotarsus are facultative pollen feeders on grasses and other plants.

Diagnosis. Species of Axinotarsus are recognized by the combination of tarsomere 2 of the male foretarsus prolonged apically as a free lobe over tarsomere 3 ( Fig. 3 ), with the lobe bearing an apical comb of stout black setae ( Fig. 3 ); an 11-segmented antenna inserted between the eyes; and the elytral apex appendiculate in males ( Fig. 4 ). Among North American genera of malachiine melyrids, Axinotarsus is most similar to Attalus . Species of both genera have tarsomere 2 of the male foretarsus prolonged as a dorsal lobe over tarsomere 3, erect hairs on the elytra, and the last maxillary palpomere fusiform and narrowly truncate. In Attalus , however, the antennae are inserted anterior to a preocular line of the eyes, whereas in Axinotarsus the antennae are inserted between the eyes. In addition, the elytral apices are unmodified in both sexes of Attalus , but appendiculate in males of Axinotarsus .

Two additional Old World congeners superficially resemble A. pulicarius in size and general coloration. Axinotarsus ruficollis (Olivier, 1790) has the pronotum entirely red, with the body weakly metallic blue or green. The similar Axinotarsus marginalis (Laporte de Castelnau, 1840) can be separated from A. pulicarius by the black median band of the pronotum more broadened behind the middle, much broader toward the base (cf. pronotal band not or only slightly broadened at middle in A. pulicarius ) and by the differently shaped apical abdominal (excitatory) appendages of the male (cf. Evers 1979: 69, figs. 2, 3).

Description. Length 2.75–3.75 mm. Pronotum reddish yellow with a broad black median band. Head and elytra shiny, bright slate gray to nearly black, occasionally with a vague green or blackish-green reflection, clothed with fine grayish pubescence. Apex of elytra broadly yellowish. Mouthparts yellowish. Black median band on pronotum not or only weakly widened at middle, normally not attaining anterior margin of pronotum. Elytra obsoletely, finely punctured; vestiture of decumbent silvery gray pubescence and erect black setae. Legs black; tarsomeres 1–4 reddish yellow, apices somewhat infuscated; tarsomere 5 mostly black.

Male ( Fig. 1 ): Antennal scape mostly black; remaining antennomeres reddish yellow, except antennomeres 2– 4 partially black dorsally and others with only apices infuscated dorsally. Elytra deeply and bluntly inflexed at apex with small black excitatory appendages ( Figs. 1, 4 ); the morphology of these appendages is described and illustrated by Evers (1948: 150, figs. 1–5).

Female ( Fig. 2 ): Antennal scape black; remaining antennomeres dark reddish yellow ventrally, darkly infuscated dorsally. Elytral apex unmodified ( Fig. 2 ).

Distribution. Axinotarsus pulicarius is a circum-Mediterranean species but is widely distributed in the western Palearctic Region. It is recorded from Austria, Belgium, Czech Republic, Denmark, France, Germany, Great Britain, Hungary, Italy, Latvia, Malta, Netherlands, Norway, Poland, Portugal, Russia, Slovakia, Spain, Sweden, Switzerland, and Ukraine (“Caucasus”) in Europe, and Algeria and Morocco in North Africa ( Mayor 2007).

Biology. In its native European range, A. pulicarius feeds on pollen of perennial grasses, mainly Holcus lanatus and Dactylis glomerata L. (orchardgrass) ( Horion 1953; Zahradnik 1985, 1990). Both grass species are adventive and widespread in the BC Lower Mainland (Klinkenberg 2011). Fowler (1890) noted the collection of this species in the British Isles “by sweeping Umbelliferae” ( Apiaceae ).

Males of A. pulicarius , as in several other malachiine melyrids, possess apical elytral appendages ( Figs. 1, 4 ). Females feed on these excitatory glands during pre-copulatory courtship ( Evers 1948; Matthes 1962). Our brief description of courtship and copulatory behavior is taken from studies by Matthes (1970 and http://www.l3s.de/ eleonet/doi/iwf/E-1747.xml). The male initiates courtship and mating by displaying his excitatory organ to a female; she tastes the male’s glandular secretions, which inhibits her initial aversion to mating. Both sexes engage in frontal tapping, using antennae and front legs; the male turns 180° and the female bites the organ. As pairing advances, the female turns her posterior toward the male, and he places his mouthparts on the tip of her abdomen. She either allows copulation, which lasts briefly, or frontal tapping is resumed.

Figures

FIGURES 1 – 4. Axinotarsus pulicarius (F.). 1, dorsal habitus, male. 2, dorsal habitus, female. 3, male protarsus (note: prolonged tarsomere 2, arrow). 4, male abdominal apex and abdominal (excitatory) appendages.