Rhaphium signiferum (Osten Sacken), 1878

Runyon, Justin B., 2022, Nematode-induced demasculinization of Nearctic Dolichopodidae (Diptera) with five new synonyms, Zootaxa 5092 (5), pp. 545-558 : 551

Rhaphium signiferum (Osten Sacken), 1878

( Figs 20–26 )

Rhaphium signiferum (Osten Sacken), 1878: 242 .

Nematode. Apparent Mermithidae .

Demasculinized male examined. 1 ♂, USA, Pennsylvania, Centre Co., Black Moshannon State Park, Moss- Hanne Trail , Shirks Run , 580 m, 20 June 2007, JB Runyon ( MTEC) .

Remarks. The demasculinized specimen was initially thought to represent an undescribed species. Recognition that two species of Dolichopus from this site were infected by mermithid-like nematodes ( D. dorycerus and D. sincerus ) spurred re-examination that indicated this specimen to be a demasculinized form of R. signiferum , a common species at the site. The genitalia of the infected specimen is smaller and not fully centered beneath the abdomen. Most MSSCs are weakly developed in the infected specimen, including: postpedicel shorter with longer arista and smaller apical lamella (cf. Figs 20, 21 ), face broader (cf. Figs 24, 25 ), postocular setae scarcely flattened, mid coxa with poorly developed cluster of fused apical setae (cf. Figs 22, 23 ), weak development of longer white setae on front and mid femora, and smaller apical swelling of the front basitarsus.

Figures

FIGURES 20–26. Comparison of normal male of Rhaphium signiferum (Osten Sacken) versus male infected by mermithid-like nematodes, and female. 20. Antenna, normal male. 21. Antenna, infected male. 22. Mid coxa (lateral view), normal male. 23. Mid coxa (lateral view), infected male. Note reduced development of apical setae. 24. Head of normal male. 25. Head of infected male. 26. Head of female.