MAYFLIES, DUNS AND SPINNERS 249 



The nymph of the blue-winged olive is included by 



Pictet under the heading of 

 Nymph of blue-winged larves rampantes or crawling 

 olive. nymphs, and is drawn in 



Fig. 41 on page 233, and there 

 given as the type of nymphs of this class. It is so 

 different in marking and form that any student can, 

 at a glance, distinguish it from the digging mayfly 

 nymph, the flat march brown nymph, or the swimming 

 nymph, in which class are included the immature forms 

 of the olive, iron-blue, and pale watery duns, the latter 

 whether Baetis binoculatus, B. scambus, Centroptilum 

 luteolum, or C. pennulatum. 



The male blue-winged olive is shown in Plate XXIV, 



and the head of the male 

 Blue-winged olive. and ventral view of abdominal 



forceps are also, in the same 

 plate, drawn to a greater degree of magnification. 

 The features by which it can be readily distinguished 

 from either of the o.ther duns are the presence of 

 three setae, the numerous cross veinlets on the wings, 

 and the shape of the hind wings. It will be seen, 

 too, that the wings are somewhat longer in propor- 

 tion to the length of the body than in any of the 

 preceding species of Ephemeridse. Nos. 22 and 23 

 in the new patterns represent the male and female 

 respectively. 



The spinners of the blue-winged olive are called 

 sherry spinners, and their habits in reference to ovi- 

 position are quite different from those of the other 



