Seasonal DimorpJiism in Bnttcrfiics. 217 



species which are either known to be characteristic of the 

 seasons in other parts of the range of the species, or which 

 at least are analogous with proved cases of seasonal 

 dimorphism. 



4. Some of these cases of simultaneous occurrence are 

 undoubtedly due to an overlapping at the change of 

 seasons. In other instances the intermingling of the 

 different forms takes place indifferently all the year roimd. 

 This is perhaps more especially apt to occur in regions 

 where the climate does not show very well-marked 

 alternations between wet and dry. 



5. Mr. Marshall has proved the specific identity of the 

 following pairs of forms by actually breeding one from the 

 other : — {a) Tcracolas toi)lia, Wallgr., and T. auxo, Luc. ; 

 (&) Teracohbs achine, Cram., and T. antevipi^e, Boisd. ; (c) 

 Teracohis omphale, Godt., and T. theogone, Boisd. ; {d) Terias 

 scnegalensis, Boisd., and T. Mhio^nca, Trim. ; (c) Byhlia 

 gotzius, Herbst {mlgaris, Stand.), and B. achcloia, Wallgrn.; 

 (/) Byhlia ilithyia, Drury, and the African form of B. 

 simplex, Butl. In each of these cases it was already 

 known that the different forms were respectively associ- 

 ated with different seasons, but the actual proof of specific 

 identity afforded by " breeding through " had hitherto 

 been wanting. 



6. The final stage can in many cases be influenced by 

 the artificial application of heat or moisture during the 

 pupal condition. Thus, Mr. Marshall has found that dry 

 warmth may cause the early wet-season form of Byhlia 

 ilithyia to approach the dry-season type of coloration ; 

 while the intermediate or early dry-season forms of 

 Pinacopteryx pigca and Crenis hoisduvalii were slightly 

 affected in the same direction. Warmth in conjunction 

 with moisture produced in early dry-season forms a 

 tendency to revert to the garb of the rains. This was well 

 seen in Teracolus achine, and to a less extent in T.phlegyas 

 and T. omphale. On the other hand, neither the early 

 Avet-season form of T. «/Micy (1896), nor the early dry-season 

 forms of several other species (1901) seem to have been 

 affected by the application of moisture without the addition 

 of heat, though a tendency towards tiie wet-season form 

 made itself apparent under these conditions in Pinacopteryx 

 pigea and, to a slighter extent, in Crenis hoisduvalii. 



7. Mr. Marshall has now detected constant differences in 

 the respective larvae and pupse, which prove that Byhlia 



