94 MR. R. TRIMEN ON BUTTERFLIES [Jan. 20, 



appearances under process of modification in mimicry of the genus 

 Acrcea. While the fulvous colouring and dark borders unquestion- 

 ably give this butterfly a strong resemblance to A. huxtoni, Butler, 

 as far as the upper surface goes, the spotting and colouring of the 

 under surface present (especially in the hind wings) an unmistakable 

 likeness to those of A. axina and A. atergaiis, Westwood, the 

 mimicry being further strengthened by all the details of colouring in 

 the head, body, and legs. I regard this as a most instructive case 

 of mimicry in progress, because, on both surfaces of the wings, the 

 ordinary coloration and markings of the section of Zeritis to which 

 Z. molomo, mihi, and Z. aranda, Wallengr., belong would appear 

 to have afforded the obvious material on which natural selection has 

 worked to bring about the very decided, though still incomplete, 

 likeness to Acrcea, the lengthening of the fore wings materially 

 assisting in producing the effect required. 



Genus Al^na, Boisd. 



78. Al^na amazoula, Boisd. 



Acrcea (Alcena) amazoula, Boisd. App. Voy. de Deleg. dans I'Afr. 

 Aust. p. .391. n. 60 (1847). 



Okavango River (December). One female example. 



This is the most northern and western station known to me for 

 this species. Other tropical localities for it are Bulawayo in Mata- 

 bele-land, and Umfula River in Mashuna-land, whence examples 

 have been sent to me by Mr. F. C. Selous. 



Family Papilionid^. 



Subfamily Pierin-e. 

 Genus Terias, Swains. 



79. Terias brigitta (Cram.). 



2 . Papillio brigitta. Cram. Pap. Exot. iv. t. cccxxxi. ff. B, C 

 (1780). 



Onircra (August), Ehanda (August-September), Humbe (Octo- 

 ber), and Okavango River (December). Twenty-two examples ; 

 ten males and twelve females. 



One of the three males from Ehanda has the underside with- 

 out any tinge of rufous, and resembling that of the ordinary male 

 zoe, Hopff., in tint, but the markings are almost obsolete. 



80. Terias zo£, Hopff. 



$. Terias zoe, Hopff., Monatsb. Akad. "Wissensch. Berl. 1855, 

 p. 640 ; and Peters, Reise Mossamb., Ins. p. 3G9, t. xxiii. ff. 10, 

 U (1862). 



Omrora (August and November), Ehanda (September), Humbe 

 (October), and Omaramba-Oamatako (January). Seven male 

 examples. 



