Larvae

3 s YSTEMATICS, BI OLOGY A ND ECOLOGY OF G ENERA A ND SPECIES OF THE

This Chapter contains written descriptions. For a numerical evaluation see the tables in Chapter 9. Information given under the genus name is not repeated under the entries for the species. Only additional species-specific information is given under the species names.

Aagaardia Saether, 2000

The two European species are known only from Scandinavia and are not treated in this book.

Acamptocladius Brundin, 1956

systematics and identification Two species have been described in Europe: A. submontanus (Edwards, 1932) and A. reissi Cranston & Saether, 1982. Males, females and larvae are keyed in Cranston & Saether (1982). Both pupae are described in Langton & Visser (2003). However, the differences between the two species are small in all stages and we found specimens of all stages that were more or less intermediate. These species may be synonymous (see also Bitušik, 2000: 53).

distribution in europe and the netherlands Both species of Acamptocladius have been reported from just a few countries, but these findings are scattered over northern, southern, eastern and western parts of Europe (Saether & Spies, 2010). In the Netherlands there are records from at least seven localities in the provinces of Noord-Brabant, Drenthe and Overijssel (e.g. Duursema, 1996; own data). Exuviae from Overijssel (Bergvennen) have been identi- fied by P. Langton as A. reissi.

life cycle Adults, pupae and prepupae have been collected in spring and late summer, suggest- ing at least two generations a year. At the end of November we found all larvae in second and third instar, probably in diapause.

microhabitat The larvae are found between plants or Sphagnum and on bottoms with organic mat- ter (own data).

water type and pH Cranston & Saether (1982) reported occurrence of the larvae in moorland lakes, a peat pool and some acid ball clay pools (pH 4.0–6.3). All Dutch records are from acid moor- land pools with pH (so far as is known) between 4 and 5. In the Pripyat region in Bela- rus we collected a male and some larvae in several pools at pH values from 6.1 to 7.5.

22 Orthocladiinae - Systematics, biology and ecology

Acricotopus lucens (Zetterstedt, 1850)

Acricotopus lucidus Brundin, 1949: 695; Pankratova, 1970: 207–208, fig. 127 systematics and identification In the Palaearctic region only one species of the genus is known (Hirvenoja, 1973). All stages can be easily recognised. The adult male has a rather high antennal ratio (about 3); the AR of approx. 2 mentioned by Hirvenoja (1973) is a mistake. In the the sclerotisation of the posterior side of the procercus and the dark occipital sclerite are especially striking. The function of the beard near the ventromental plates is unknown. distribution in europe and the netherlands A. lucens has been collected across almost the whole of Europe, but seems to be absent from some parts of the Mediterranean area (Rossaro, 1982; Saether & Spies, 2010). In the Netherlands the species is common in most of the country, but scarce in the prov- ince of Zeeland (Nijboer & Verdonschot, unpublished; Limnodata.nl). life cycle The adults from March to October (Hirvenoja, 1973; own data). The life cycle is not known in detail, but most probably there are several generations in spring and sum- mer and a larval diapause in winter. There are some records of fourth instar larvae in January. swarming We observed once a small swarm of this species at the water’s edge near the vegeta- tion, at a height of 50 cm. feeding Based on a study of larval gut contents, the larvae seem to prefer diatoms and filamen- tous algae as food, but they also feed on detritus (A. Klink, unpublished; own data). microhabitat The larvae live mainly on plants, sometimes near the water surface on floating leaves OR of Glyceria, Nuphar, Lemna and Azolla or between filamentous algae. Higler (1977) found the larvae scarcely on Stratiotes. They also live on organic bottoms and on stones, and are often collected in pools and ditches with much detritus, especially on peaty bottoms (Hirvenoja, 1973: 74; own data). water type Current The larvae live in stagnant and slowly flowing water; see table 7 on p. 286. Records from fast-flowing streams, as in Orendt (2002a), are undoubtedly larvae that have been carried from slow-flowing stretches or oxbow lakes. Moller Pillot (2003) stated that A. lucens was a typical habitat-shifting species in a small lowland ecosystem, in winter surviving in (often temporary) ditches and in summer shifting to the upper course of a lowland brook when the water flow there decreased, pH increased and vegetation became denser. Further downstream the larvae were only common in drift samples.

23