Parallelomma paridis
According to Collin (1958)[1] the third antennal joint is darkened (clear yellow in P. vittatum) and the terminal bristle on the palps is stronger than the vibrissae (not as strong in P. vittatum). Hackman (1957)[2] illustrates paler markings on the thoracic dorsum which Nelson (1990)[3] confirms were present in his reared specimens, but cautions that teneral P. vittatum also showed similar markings. Nelson (1990)[3] suggests that the most reliable way of distinguishing the two was to measure the terminal bristle on the palps which was 0.38-0.49 mm in P. paridis compared to 0.24-0.38 mm in P. vittatum. Wing length: ♀ 4.4 mm (1).
References
- A short synopsis of the British Scatophagidae (Diptera). Transactions of the Society for British Entomology, 13, pp.37-56., 1958.
- The Scatophagidae (Dipt.) of Eastern Fennoscandia,. Fauna Fennica, 2, pp.1-65., 1956.
- Observations on the biology and status of British dung-flies of the genus Parallelomma Becker (Dipt., Scathophagidae). Entomologist's monthly Magazine, 126, pp.187-189., 1990.
Larvae mine the leaves of herb Paris (Paris quadrifolia) and the mines are illustrated by Séguy & Pauchet (1929)[1]. Some continental literature also mentions Solomon's seal (Polygonatum) and other liliacous plants, but given the confusion over the nomenclature of this genus, it is not at clear that this refers to the same species. Nelson (1990)[2] found the average number of eggs laid on a leaf was 4.9 and the larval development was rapid, taking only 13 days. The species appears to be univoltine and to spend most of its life as a pupa (average 348 days). Adults hatched in May which fits with previous field records of adults which range from late April to late May.
References
Recorded from Berks, Cambs (Wooditton Wood - now coniferised and unlikely to be suitable), Yorks, Cumberland, Stirling, Perth and Forfar. Nelson (1990)[1] doubts that this species is a scarce as previously thought and reports that he has found it wherever he has been shown the host plant (which is itself quite scarce). Localities with herb Paris should be checked for evidence of larval mines since the rather short flight period may makes adults difficult to detect.
World distribution: Palaearctic: Denmark, Lithuania, Sweden; Russia: Karelia; Indomalaysian: Nepal.