Melanogaster hirtella Loew, 1843:251

Chrysogaster hirtella Loew, 1843.

Loew, H. (1843) Bemerkungen uber die bekannten europaischen Arten der Gattung Chrysogaster Meig. [Stettiner] Entomologische Zeitung 4(7), 204-212; (8), 240-255; (9), 258-281.

Flowers visited by adults: white umbellifers; Caltha, Euphorbia, Iris pseudacorus, Menyanthes, Mimulus guttatus, Potentilla erecta, Pyrus communis, Ranunculus, Sorbus aucuparia, Taraxacum, Viburnum opulus (Speight 2010).

The flight period for this species is from the end of April to July and on into August at higher altitudes (Speight 2010).

C. hirtella ranges from Denmark south to the Pyrenees and Portugal; Ireland eastwards to the Alps (Switzerland, Liechtenstein). This is very much an "Atlantic" species, very widespread and abundant along the western seaboard of the continent from Denmark to Brittany, but otherwise rather localised and increasingly scarce as one progresses into central and southern Europe (Speight 2010).

Adults can usually be found in the vicinity of standing or running water, flying among field-layer vegetation and settling on leaves or flowers (Speight 2010).

Preferred environment: wetland, fen, marsh, poorly-drained pasture and a wide range of waterside situations, such as along woodland streams or field drains, beside lakes, ponds and rivers, up to the altitude of Picea forest (Speight 2010).

Larva of C. hirtella was described and figured by Hartley (1961); aquatic, associated with various aquatic plants, including Glyceria and Typha, whose aerenchyma is tapped by the larvae to provide their air supply; the larvae are to be found among plant roots, usually at the edge of running water, in the angle where the bank begins to rise away from the water level.

Third instar larva (from Hartley 1961).

Length, 8 mm; breadth, 2.5 mm. Shape similar to C. solstitialis. Cuticle colourless, slightly warty; pubescence well developed on ridges only; fewer, larger spinules posteriorly; absent or nearly so ventrally; ventral area bounded by conspicuous fringe of spinules along the ventro-lateral line; chaetotaxy as shown; prothorax with D4 and D5 separate; D1 with pair of long setae, others with short rosette of setae; meso- and metathorax with D1 and D2, D4 and D5, and L1 and L2 all separate. Setae large posteriorly on small papillae except on A8 where the posterior-laterals are on stout, short lappets. Prolegs and crochets as C. solstitialis. Posterior spiracles stylet-like (Hartley 1958) at end of short telescopic breathing tube which can be extended about 2 mm. Anal papillae (Hartley 1958) much branched and each branch further subdivided into numerous branchlets, formula probably 6 : 6 : 8 : 4.

Puparium (from Hartley 1961).

Length, 6 mm; breadth, 2.5 mm. Shape as C. solstitialis; spiracles (Fig. 66), up to 2 mm. long, pale, finely tuberculate, slightly curved; cuticle pale brownish, transparent, with conspicuous dark ring round each, spiracular window.

Taxonomic notes: This species is distinct from others' of the genus except. C. macquarti on account of the root-piercing spiracle; with the adults C. macquarti can only be definitcly distinguished from C. hirtella by the genitalia, and the larvae are probably indistinguishable.

Biological notes: It was known previously that the second and third instars had stylet-like spiracles which are used for piercing roots and obtaining air in this way (Hartley 1958 ; Varley 1937 (third instar only)). The first instar also has stylet-like spiracles, 0.2 mm long with stylet 0.15 mm The eggs are 1 mm long and are laid in batches on the underside of vegetation overhanging the breeding place. Probably only one generation occurs in a year, overwintering as larvae. The larvae are associated with various aquatic and semi-aquatic plants including Glyceria and Typha. The species lives in rich organic mud or silt and has been found near the edges of ponds and slow streams. Pupation takes place on objects raised above water level.