Seasonal Bimorjyhism in Butter Jlics. 217 



species which are either known to be characteristic of the 

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

 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 round. 

 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) TcracoUis topha, Wallgr., and T. aiuvo, Luc. ; 

 {h) Teracohis achine, Cram., and T. antcvippe, Boisd. ; (c) 

 Tcracolus omphale, Godt., and T. theogonc, Boisd. ; {d) Terias 

 senega! ens is, Boisd., and T. c'Bthiopica, Trim. ; (e) Byhlia 

 gotzms, Herbst {vulgaris, Staud.), 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 bo influenced by 

 the artificial application of heat or moistui'e during the 

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

 warmth may cause the early wet-season form of Byhlia 

 ilithyia to approach tlie dry-season type of coloration ; 

 while the intermediate or early dry-season forms of 

 Pinacopteryx pigea 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.pldegyas 

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

 wet-season form of T. annm (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 the wet-season form 

 made itself apparent under these conditions in Pinaeoptcryx 

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



7. Mr. Marshall has now detected constant differences in 

 the respective larvae and pupae, which prove that Byhlia 



