Macroplea pubipennis (Reuter 1875), Chrysomelidae

Compiled by: Terhi Ryttäri & Ilpo Mannerkoski, Finland

1. Description / Ecological demands / Autecology

Macroplea pubipennis is a 6-7 mm long, straw-colored chrysomelid beetle with long legs and antennas. It differs from a close relative M. mutica only by the shape of elytral apex and the male genitalia. It lives in shallow waters, at a depth range of 25-50 cm, usually in sheltered bays. This herbivore beetle is known to feed on submerged aquatic plants, such as Potamogeton, Myriophyllum and Zannichellia species. It lives underwater throughout its life cycle, but the details of its biology, especially in larval stages, are poorly known. The adult beetles crawl together, the smaller male "riding" on females' back. M. mutica lives usually on same places.

2. Distribution

In Europe, M.  pubipennis is known to live only in the northern parts of Baltic Sea. Observations have been made along the coasts of Finland from the Gulf of Finland up to the Bothnian Bay – at the moment besides some stray observations only two populations are known, one in the Gulf of Finland and one in the Archipelago Sea. Globally, the species is rare and known to have a very disjunct distribution. Observations have been recorded under another name, M. piligera Weise from Central Asia – but it is not known for sure whether the same taxon is in question.

3. Importance

M. pubipennis is a globally rare species which has at the moment at least two viable populations in the Baltic Sea. The beetle is included in the Habitats Directive Annexes II and IV.

4. Status of threat

In its known distribution area in Finland M. pubipennis is classified as vulnerable and it is listed as a species under strict protection in the Nature Conservation Degree.

5. Threat factors

M. pubipennis is threatened by dredging and construction. Disturbance caused by boat traffic, changes in water quality as well as changes in vegetation due to eutrophication (mainly expansion of reeds) are unfavourable to this species.

6. Conservation measures needed

Unsuccessful searches of M. pubipennis have already been carried out in Estonia and Sweden. Despite of this, inventories are needed to find out the actual distribution of, and threats to, M. mutica in the Baltic Sea. More research on the ecology of the species is also needed. The most important known populations are already partly protected. Newly discovered sites should be protected as well and all harmful human activities should be prohibited there.

7. References:

Biström O. 1995: Kartering av stor natebock, bladbaggen Macroplea pubipennis (Coleoptera: Chrysomelidae) i Esboviken, Finland. (Mapping of the leaf beetle species Macroplea pubipennis in the Esbo Bay, Finland) – Sahlbergia Vol. 2:113-116. (in Swedish)

Ilmonen J., Ryttäri T. & Alanen A. (eds.) 2001: Finnish plants and invertebrate animals in the EU Habitats Directive. A scientific evaluation of the Finnish Natura 2000 –proposal. – The Finnish Environment 510: 1-177. (in Finnish)

Rassi P., Alanen A., Kanerva T. & Mannerkoski I. (eds.) 2001: Suomen lajien uhanalaisuus 2000 (The 2000 Red List of Finnish species). – Ympäristöministeriö & Suomen ympäristökeskus, Helsinki.