Procladius (Holotanypus) denticulatus Sublette, 1964

Egan, Alexander T. & Langton, Peter H., 2018, DESCRIPTIONS OF FOUR NEARCTIC PROCLADIUS SKUSE PUPAL EXUVIAE Abstract, CHIRONOMUS Journal of Chironomidae Research 31, pp. 30-36 : 34-35

Procladius (Holotanypus) denticulatus Sublette

Material examined. USA: New Hampshire, Mirror Lake, 14-24-VI-74, reared male, col. Rhoda Walter.

Pupa (n = 1). Total length 5.45 mm.

Cephalothorax. Thoracic horn 420-430 µm long; 100-110 µm wide; with teeth; atrial wall with weak reticulation; plastron plate length 50 µm, width 90 µm; apical constriction of horn chamber 62 µm wide; length/width of horn 3.9-4.2; width of plastron plate/width of horn 0.82; width of plastron plate/width of constriction 1.45 ( Fig. 12 ).

Abdomen. Tergites with color pattern 3, minimal contrast. Shagreen of T IV medially with small points (1-2 µm, Fig. 13 ) often arranged in short rows and smaller than median points on T VIII (3-4 µm). LS taeniae of VII at 0.62, 0.81, 0.93, 0.98 segment length. LS taeniae of VIII at 0.30, 0.50, 0.67, 0.83, 0.93 segment length. Anal lobe length 530 µm; 29 spines on outer margin; largest spines (33-37 µm) posterolateral with gaps wider than the base of the spines; anterior and apical spines smaller (as small as 5 µm), more closely set, with one apical spine on a small protuberance apically ( Fig. 14 ).

Remarks. Separating this species from P. signatus , which has been suggested as a possible senior synonym ( Roback 1971), is difficult since the two species are exceedingly alike. Including an additional three specimens (collected by W. P. Coffman and D. Oliver) to the one described here, we observe that on the whole P. denticulatus is smaller (ThL 400-430 µm), whereas P. signatus is larger (ThL 480-624 µm, mean = 546, n = 13). Roback (1980) gives the range for P. denticulatus ThL as 370-540 µm (mean = 468) and Saether (2010) a ThL range of 393-577 µm (mean = 469), so there is overlap. However, the means are well separated so ThL should be a useful feature unless a specimen falls into the intermediate range and geographic provenance is unknown. Size may be useful for total exuviae length as well, with a range of 5.7-8.5 mm (mean = 6.6) for P. signatus (Langton 1991) .

In addition, points on tergite IV are smaller on P. denticulatus (1-2 µm), which are smaller than on tergite VIII (3-4 µm), whereas points on the two tergites for P. signatus are of similar size (4 µm, Langton 1991). This feature is independent of exuviae size. A final structural difference that may hold for P. signatus is that the strong points of the thoracic horn wall continue over the ‘shoulder’, where the horn constricts apically, and onto the ‘hood’, the apical region containing the plastron plate ( Fig. 15 ). In contrast, P. denticulatus points on the hood are reduced in size and density.

Procladius denticulatus is widespread in the northern Nearctic.

Figures

Figure 15. Procladius signatus, apex of thoracic horn.

Figures 12-14. Procladius denticulatus. 12, thoracic horn (Scale = 0.1 mm); 13, tergite IV medial shagreen (Scale = 0.025 mm); 14, segment VIII and anal lobe (Scale = 0.1 mm).