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Beech Longhorn Beetle

(Morimus asper funereus)

Morimus is a genus of Cerambycidae (longhorn beetles) that, based on morphological differences such as the colour, spotting and granulation of the elytra (wing case), was once considered to comprise 5 distinct European species. However, a recent molecular study found that all European members of the genus belong to a single morphologically variable species Morimus asper, comprising three subspecies Morimus asper asper, Morimus asper funereus and Morimus asper verecundus.

 

Morimus asper funereus

 

Morimus asper has been described as 'chromatically variable throughout its range', with the subspecies Morimus asper funereus distinguished from the other subspecies by its light bluish grey elytra, which bears four very distinct black spots. This also helps to distinguish the species from another longhorn beetle Herophila tristis, as do antennal differences. 

In Herophila tristis the first antennal segment is longer or equal to the length of the third segment: 

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In Morimus asper the first antennal segment is noticeably shorter than the third segment:

https://commons.wikimedia.org/wiki/User:Sigahttps://commons.wikimedia.org/wiki/User:Siga

 

A conspicuous sexual dimorphism exists in the antennal length of Morimus asper, as in many other longhorn beetles, with male antennae much longer than those of females, and measuring up to 7.5 cm, and thus exceeding the length of their body, which is typically between 1.5 to 4.0 cm. The length of the antennae varies greatly among males from the same population, and it is thought at males with longer antennae mate more frequently.

 

Morimus asper

 

Morimus asper is a silivicolous, xylophagous and saproxylic species, mainly inhabiting old-growth forests or well-structured woodlands, with a medium-high density of dead wood. Females oviposit in dead wood with bark still attached, with a preference for large standing trees, trunks on the ground and large stumps. The species is typically found in deciduous and mixed forests, and for many areas of Europe, a preference for oak (Quercus spp.) and beech (Fagus spp.) forests has been reported. It lives over a wide altitudinal range, and the phenology of local populations is related to altitude. In Italy, this species has been recorded from sea level up to a maximum altitude of 1870 m. In Bulgaria, it is said to be particularly common in mountain beech forests, rather than those in the lower hills and plains, and has been recorded up to 1800 m. During our own researches in the Rodopi Mountains, we have found Morimus  asper between 410 to 1040 m, with the average altitude of records being 735 m. 

 

Morimus asper

 

Morimus asper is flightless, on account of its reduced hindwings and fused elytra (wing case), and this markedly reduces its dispersal abilities when compared to other longhorn beetles, and thus its populations are often fragmented, and it is frequently unable to colonize otherwise suitable habitats. The subspecies Morimus asper funereus has, therefore, been included in Annex II of the the Habitats Directive, and when considered a separate species, was classified as Vulnerable in the IUCN Red List of Threatened Species.

 

Morimus asper

 

Adults of Morimus asper are relatively long-lived and can overwinter to reproduce for a second year. In captivity, the oldest specimen survived up to 560 days. The period of the year when adults are active is quite long when compared to other insects, but seems to be variable. In Bulgaria, adults of the species have been reported as active between April and August, with all our own records in the Rodopi Mountains coming from the months of May and June. In Slovenia, two peaks of activity have been observed, the first from the end of May to early June and the second between the end of July and early August, suggesting that the second peak was the result of freshly emerged specimens. A citizen science survey in Italy, meanwhile, recorded the species between 8 January to 29 October, with largest numbers between mid-April to mid-August. Particularly interesting was the fact that the activity peak was observed later at higher altitudes. Several studies report that Morimus asper is mainly active in the evening and during the night; however, it is not uncommon to find adults active during the day, and this seems to be connected to seasonal temperature differences, with 12–30°C being suggested as the temperature limits of the species' activity. 

References:

* Bringmann, H. D. (1996) Die Morimus- und Acanthoderes- Arten Bulgariens (Col., Cerambycidae). Entomologische Nachrichten und Berichte 40(4): 237–239.

* Hardersen, S., Bardiani, M., Chiari, S., Maura, M., Maurizi, E., Roversi, P. F., Mason, F. & Bologna, M. A. (2017). Guidelines for the monitoring of Morimus asper funereus and Morimus asper asper. Nature Conservation20: 205-236.

* Solano, E., Mancini, E., Ciucci, P., Mason, F., Audisio, P., & Antonini, G. (2013). The EU protected taxon Morimus funereus Mulsant, 1862 (Coleoptera: Cerambycidae) and its western Palaearctic allies: systematics and conservation outcomes. Conservation Genetics, 14(3): 683-694.