IN-hCTS OF REVERSED BKHAVlnR. 395 



in the mating flights in the deep shade of the mountain gorges 

 as its visibility i- very obviously increased by this color pattern. 

 A snuff-colored, lowland Ephemera would be practically in- 

 visible under the same conditions. It is interesting to note 

 that of several species of mayflies flying on these stream- at this 

 time guliulaia is the latest on the wing in the evening and flies 



r the other- have ceased. Some of the smaller specie- lly 

 a full hour earlier, so that, though, of dull colors they are quite 

 \ i-ilile. 



\Yecan (link ihi- -cries of reactions of giittulata by a compari- 

 -oii with tin- UK tions of the other species of Ephemera, all of 

 which inhabit, either large open streams or lakes. Probably the 



cm era simulans, the common Lake Erie S] 



.ire br-,t known. The nymph of this species burrows in the 

 mud of the lake bottom, being obviously negatively phototropic. 

 At the time of emergence it becomes positively phototropic .ind 

 < the light of the sky. At Put-in-Bay this emergem v 

 take- pi. ice between eight and ten P.M. It sheds its skin as 

 it rises through the ten to thirty feet of water so that on arrhal 

 at the surface it bursts out fully winged, when it becomes le 



ti\ely phototropic and flies toward the dark land. It n 

 on the shore vegetation until the following evening when it 

 -linl- it- final -kin, becomes sexually mature and at twiliJit 

 flutter- up and down in the mating dance. At this stage it i- 

 e\i<lently !>e<i>ming positively phototropic again. In this twi- 

 light nuptial dance it leaves the dark foliage for the more open 

 lighter spaces. The males grasp the females and release them 

 after a emit.. i few seconds. The female becomes at om e 



ciiinpletely. pi.-iti\ely phototropic and flies out toward the light 

 -urfai e of the lake to deposit her eggs. 



It \sc compare this series of reactions with those of guttitlntu 

 of the -haded mountain streams, we find that two of the seric- 

 i.f rea< nn- of the latter are reversed. Giittulata is n-vati\el\- 

 phototropic as a nymph, is positive as it emerges, but remains 

 /'"s///i'c/v phototropic after emergence as it flic- from the heavily 

 shaded creek to the lighter areas above the sliadr. further, 



r copulation it becomes negatively phototropii and flies down to 

 tin clcn-cl\ -haded torrent to oviposit. Any of the open >tream 

 species f Kphcmera would react them-elvc- a\\a\ from the 



