222 Dr. Fritz Miiller's Notes on 



ratlier louder, produced by two small brown butterflies, 

 which seemed to be Euptycliia, but which I did not 

 succeed in catching. 



It has been suggested that the production of sound bj 

 Ageronia is connected with the existence of a small mem- 

 branous sac at the base of the front wings, which in the 

 living insect is filled with air when the costal nervure is 

 compressed. But this sac also exists in several other 

 butterflies, which seem to be incapable of producing 

 sounds, e.g., Pgrrhogyra Edocla and CalHcore Eluhut. 

 If I remember rightly, in Eiinica Margarita the sac is 

 wanting. 



Insects distinguishing Colours. 



In flowers with changing coloiu'S, most of the visiting 

 insects perfectly distinguish the first honey-filled flowers, 

 as I have ascertained by a long series of observations on 

 some species of Lantana. In some species the difference 

 in colour between the fresh flowers and the older ones is 

 but very trifling, a small yelloAV circle surrounding the 

 entrance to the tube of the corolla during the first day and 

 disappearing afterwards. 



A specimen of Victorina Frayja w^as lately observed 

 settling on the flower of a rose-tree painted on a Avail ; the 

 painter was much pleased by seeing his skill thus acknow- 

 ledged by that butterfly. 



Mimicry. 



In some years, as I stated in 1871, Mechanitis Lysimnia 

 is here hardly more common than the imitating Leptulis 

 Astynome ; but in most years M. Egsimnia is extremely 

 abundant and L. Astynome rather rare. 



When I descended in a canoe the western branch of 

 the Itajahy (December 16th, 1876), small white butterflies 

 were very common on the banks of the river : all appeared 

 to be of the same species. I caught about a dozen, and 

 on examining them at home found them to be Leptalis 

 Nehemia, w'hich so wonderfully mimics a Pieris, that 

 even Boisduval w^as deceived and described it as Pieris 

 Nehemia. Now, in his case, the model must have been 

 either by far more rare than the copy, or entirely wanting. 



On the Itajahy we have three species of- Eueides, viz., 

 E. Pavana, Isabella and Aciphera ; all of them are rare, 

 and E. Pavana extremely so. This last species closely 

 resembles Acrcsa Thalia; E. Isabella resembles Mechanitis 

 Lysimnia and Heliconius Eucrate, while E. Aciphera 



