480 MR. A. G. BUTLER ON [Nov. 4, 



butterflies crossing the Red Sea in the very teeth ot a strong wind." 

 There would therefore be nothing very extraordinary in the flight of 

 some of the larger species across the Strait of Bab-el-Mandeb, 

 more especially if the wind chanced to be in their favour. 



Lest there should be any doubt in the minds of Lepidopterists as 

 to the specific identity of the four forms of Aden, I quote here 

 Major Yerbury's note on the species : — " I have taken dorippus and 

 chrysippus ' in coitu ' so often that I have given up catching them as 

 a curiosity : I have raised caterpillars feeding on plant no. 41 1 ; there 

 seemed no difference between the caterpillars which turned to 

 chrysippus and those that turned to dorippus. The chrysalides were 

 of two colours — green with gold spots, and light waxy purple with 

 ditto."— J. W. Y. 



From notes attached to the specimens, it would appear that the 

 green chrysalis produced the Lido-African form of L. dorippus 

 and the purplish chrysalis L. chrysippus and intergrades towards 

 L. alcippus. It is a singular fact if there really is not even a slight 

 difference between the larvae of the various forms. 



The question now arises as to what the systematist is to do with 

 these four forms, since they are (so far as is known) good species 

 everywhere, excepting at Aden. If we apply to them trinomial 

 appellations, calling one Limnas chrysippus alcippus, another Limnas 

 chrysippus dorippus, and so on, we declare that they are local races 

 of one species ; and yet as a matter of fact they both are and are not. 

 Again, supposing the trinomial system to be generally adopted for 

 local races, though it would practically (if not always immediately) 

 reduce every genus of Lepidoptera to a single species, and eventually 

 as links continued to turn up (so as to necessitate the union of 

 nearly allied genera) might lead back the lepidopterist by a process 

 of retrogression to the first described butterfly, nevertheless, though 

 all these evils might spring from the adoption of this system, Limnas 

 chrysippus and one or two other Aden butterflies could not be 

 embraced by it, because at Aden their forms are not local but mere 

 polymorphic sports, or in a word true varieties. 



In the present paper I shall keep the various named forms 

 separate, though under one number, the first as a matter of con- 

 venience, to enable me to record the exact place and date of capture, 

 the second to indicate that at Aden they are not distinct species. 



RIIOPALOCERA. 

 Nymphalid,e. 



EuPLCEINiE. 



1. Limnas chrysippus. 



Papilio chrysippus, Linnaeus, Mus. Lud. Ulr. p. 263 (1764). 

 One typical female, Aden, 26th February, 1883. 

 Taken in coitu with Indo-African type of L. dorippus. 



1 I cannot get the name of this plant. 



