Rheosmittia spinicornis

Author: (Brundin, 1956)

Diagnosis (in part after Cranston and Saether, 1986a - in italics)
Exuviae very small, 1.5-1.7mm long (n=7) (057-1.jpg); brown or brownish. (1.3-1.7mm (n=8), female shorter than male, hyaline.)
Cephalothorax: Frontal setae absent; cephalic area smooth, without warts or tubercles. Ocular area with 1 postorbital and 1 vertical seta, ocular and postorbital setae each about 40µm long. Thoracic horn absent. Thorax with 1 or 2 median and 1 or 2 lateral antepronotal setae; 3 precorneals in a line with second the longest; dorsocentrals arranged in 2 groups with seta 4 apparently absent. Anterior precorneal seta 25-34µm long, median 45-60µm long, posterior 32-46µm long. All dorsocentral setae about 40-52µm long. Thorax smooth to weakly rugulose; wing sheaths smooth; leg sheath arrangement normal for Orthocladiinae.
Abdomen: Tergite I and sternites I or I-IV and V-VIII or VII-VIII without shagreen. Tergites II-IV or III and IV with caudal, anteriorly directed points. Tergites II-VII (or (VII) with posterior transverse band of posteriorly-directed points and an antero-median area of smaller points which may extend posteriorly to contact posterior band. Median point area weaker on posterior segments and very reduced on tergites VII and/or VIII. Tergites IV-VI without a distinct circular antero-median point patch. Sternites V and VI with posterior transverse rowsof weak, anteriorly directed points. Apophyses absent. Pedes spurii A and B absent. Segment I with 2(?) weak or 5 stronger dorsal setae, 0-2 V setae and 1 lateral seta. Segments II-VII with 4 or 5 dorsal setae, 4 or 5 V setae and 3 or 4 lateral setae. Segment VIII with 2 or 4 dorsal setae, 1 V seta and 2 lateral setae. On tergites II-IV or VI dorsal seta 5 enlarged, on tergites III and IV very widely fanned out apically (057b.jpg), on III 45-56µm long, 12-15µm wide at apex. Lateral seta 2 often more strongly developed than remaining lateral setae.
Note: Specimens from Tunisia are more heavily armed with median and posterior point bands joined in a number of places, whereas those seen from northern Europe have these bands joined medially only.
Anal segment: Tergite IX medially with or without shagreen. Anal lobe very reduced with tergite IX postero-laterally expanded into spinose tails. Anal lobe, including tails, 106-148µm (m=132µm) long. Anal lobes without fringe and macrosetae. Genital sacs of male large, nearly extending to apex of tails.
(Linked adult male: Langton and Pinder, 2003a)

Species keys out at Page 749: Orthocladiinae 161 Rheosmittia of the Text Key.

Widespread in Europe, circum-Mediterranean.
(For more information see module IdentifyIt – file: Orthocladiinae).

Ecological notes