85 

 Day: Ephemeroptero 



Fig. 3:5. a, Cinygmula uniformis, male genitalia; b, Ironopsis grandis, male genitalia; c, Iron 

 sp., wings; d, Ironodes sp., nymph; e,f, anterior and posterior lamellae of third nymphal gill of 

 Iron sp.; g, Rh/'fhrogena sp., nymph, with ventral aspect of abdomen and first gill (a,b,c/,g, Need- 

 ham, Traver and Hsu, 1935; c,e,f, Spieth, 1933). 



8. Stigmatic cross veins of fore wing more or less strongly 

 anastomosed, sometimes forming 2 series of cellules; 

 basal costal cross veins weak (fig. 3:56) 



Ironopsis Traver 



— Stigmatic cross veins of fore wing not anastomosed; 

 basal costal cross veins variable 9 



9. Basal costal cross veins of fore wing weak, stigmatic 

 cross veins not slanting (fig. 3:5c) 



Iron Eaton 



— Basal costal cross veins of fore wing strong; stigmatic 

 cross veins distinctly slanting Ironodes Traver 



Nymphs 



1. Fibrillar part of each pair of gills wanting; second 

 joint of maxillary palp at least 4 times as long as 

 galealacinia Arthroplea Bengtsson 



— Fibrillar part of each pair of gills present; second 

 joint of maxillary palp much shorter 2 



2. Tails 2 3 



— Tails 3 5 



3. A triad of stout spines present at tip of galea-lacinia; 

 no submedian spines on tergites 4 



— No such triad of spines on galea-lacinia, a pair of 

 submedian spines present on tergites (fig. 3:5d) .... 



Ironodes Traver 



. Median row of long hairs on abdominal tergites; front 

 of head slightly emarginate; first gills meet beneath 



the body Ironopsis Traver 



No such row of median hairs on tergites; front of head 



not emarginate (fig. 3:5e,/) Iron Eaton 



Gills of seventh pair reduced to a single slender tapered 

 filament or spine; tracheae, if present in this filament, 



without lateral branches Stenonema Traver 



Gills of seventh pair flat and platelike, quite similar 

 to preceding pairs; tracheae with lateral branches 



always present in seventh pair 6 



Fibrillar part of gills reduced to a few viny threads; 



front of head distinctly emarginate 



Cinygmula McDunnough 



Fibrillar part of gills well developed on segments 1-6, 

 may be wanting on 7; front of head entire or very slightly 



emarginate 7 



Gills of first and last pairs much enlarged, converging 



beneath body (fig. 3:5<7) Rhithrogena Eaton 



Gills of first and last pairs not as large as middle pairs; 

 all gills directed laterally, not converging beneath 



body 8 



Labrum narrow, about 1/3 the width of anterior margin 

 of head; a chitinized area present on each mandible 



below molar region Cinygma Eaton 



Labrum broad, 2/3 to 3/4 the width of anterior margin 

 of head; no such chitinized area on mandible (fig. 

 3:6a, 6) Heptagenia Walsh 



