Psen ambiguus SCHENCK 1857; Psen intermedius SCHENCK 1857
Description and notes
There are approximately 100 species in this genus worldwide. Lomholdt (1984) states that there are only seven species in Europe, but Bitsch et al. (2001) list ten, although one of these, P. hidalgo, was only described in 1990.Three species have been recorded in Britain.
This species has been widely recorded from south-east England, with more scattered records from the south-west, the Midlands, south and east Wales northwards to Yorkshire.
Lomholdt (1984) states that this species is rather uncommon and sparsely distributed in Scandinavia, but is widespread across northern and central Europe and also occurs through southern Siberia into Japan.
Status (in Britain only)
This species is not thought to be threatened or of conservation concern.
Presumably found in a wide variety of habitats, wherever favoured nesting sites are to be found. These would include areas of reed, scrub and the thatch of old houses.
May to August.
Danks (1971) records the prey as being the nymphs of Psyllid Homopteran bugs.
Nests in hollow stems. Richards (1980) suggests a possible preference for ash trees, although this is not specifically mentioned by Lomholdt (1984), who cites more generally its nesting habits in hollow or pith-filled stems (such as common reed including the cigar galls of the Chloropid fly Lipara lucens; elder and bramble). Lomholdt (1984) also records individuals nesting in the eaves of thatched roofs and in old timbers. Bitsch et al. (2001) list ash, bramble, butterfly-bushes, elder and viburnums.
The number of cells per nest is said to vary somewhat, but 5 is deemed to be a usual number (Lomholdt 1984), with 14-24 prey items per cell.
No data available.
Lomholdt (1984) cites the hymenopterous parasitoids Perithous mediator Grav. (Pimplinae), Cratocryptus anatorius Grav. (Cryptinae) and Eurytoma nodularis (Chalcidoidea).
Year profile last updated