Paramerina pygmaea

Author: (van der Wulp, 1874)

Diagnosis (n=32, unless stated otherwise)
Exuviae 3.6-4.9mm long (m=4.3mm, n=30) (023-1.jpg).
Cephalothorax: Thoracic horn 225-330µm long (m=292µm), with rounded basal tubercle; ThR 3.7-5.9 (n=14). Plastron plate maximum diameter 15-50µm, over twice as wide as its neck; length 0.05-0.15x horn length. Rim maximum diameter 52-112µm, extending at most a third the length of the horn, to one and a half times as long as the horn is wide (023b.jpg). Atrium of thoracic horn thin-walled, joined to the plastron plate by a short straight neck. Thorax granulate. Thorax comb well-developed, composed of strong, more or less parallel-sided teeth.
Abdomen: Tergite I with a median mark. Segment VII transversely rectangular. Four lateral taeniae on segment VII, anterior lateral taenia at 0.35-0.45 of length segment VII (m=0.41, n=12). Anterior lateral taenia of segment VIII at 0.23-0.35 of length segment VIII (m=0.30, n=12).
Anal segment: Anal lobes without a thickened lateral edge, toothed externally only. Anal lobe ratio 2.6-3.8 (m=3.1). Insertion of anterior anal taenia at 0.33-0.46 of lobe length (m=0.36). (023c.jpg)
(Linked adult male: Langton and Pinder, 2003a)

Note 1: A specimen of Zavrelimyia melanura with only one obvious tooth internally on one anal lobe and two on the other suggests that melanura may even produce pupae without internal teeth on the anal lobes. In addition to the remarks above separating these very similar genera, the two species involved here may additionally be separated by the armament of sternite VII: in pygmaea the minute points anteriorly to each side of the mid-line are arranged in rather distinct transverse to slightly oblique rows, whereas in melanura these points are arranged irregularly.

Note 2: The combination of characters separating Paramerina pe1 (Langton, 1984) (023f.jpg , 023g.jpg) and pygmaea have been shown to be more variable than indicated by the small numbers seen then; however, the maximum diameter of the plastron plate still forms a bimodal distribution with increased numbers of specimens: 15-30µm (m=23.2µm, n=20) and 35-50µm (m=40.8µm, n=10), the latter representing "Pe1". It remains to be seen whether this distinction is indicative of the presence of two species or merely artifactural due to the widely separated collections of few specimens each.

Species keys out at Page 90: Tanypodinae 76 Paramerina of the Text Key.

Widespread in Europe and circum-Mediterranean.
(For more information see module IdentifyIt – file: Other subfamilies).

Ecological notes
Common in northern and montane lakes, pools and streams; local in pools elsewhere.