204 THE entomologist's kecord. 



Tutt's five belong thereto. The resemblance in size and form may 

 perhaps be in some degree seasonal — the specimens of amhu/ua which 

 appear in the height of summer being possibly inclined to favour their 

 contemporary snperstes. One of the three large ambigua was taken in 

 the same year as the two true mperstes, the other two in July, 1887, 

 and July, 1888, respectively. I may add that Mr. Tutt's two superstes 

 are not so strongly marked as some specimens T have seen, hence the 

 contrast with ambigua is less striking. 



gciENTIFIC NOTES & OBSERVATIONS. 



Discussion on the plature of certain Insect Colours. 



(Continued from page 140). 



As far as the Pieridae are concerned, we have apparently got a 

 definite pigment. I have written to Dr. Hopkins, and he tells me that 

 the uric acid derivations will dissolve in hot water, that they are 

 enclosed in a scale as in an envelope and not intimately combined with 

 the chitin, as is the case in most other Lepidoptera. With regard to 

 the excretion seen at the time of emergence of most Lepidoptera 

 (Macros at all events), it is, I believe, in every instance a nitrogenous 

 waste product, belonging to the urea, ammonia and cyanogen groups — 

 either or any of them. In some moths, e.g. Cerura vinula, the excretion 

 is at first pinkish, changed by exposure to white ; quadurate of soda 

 changed by oxidation to uric acid. The same change is to be observed in 

 the excreta of snakes.. Dr. Riding objects to the term black pigment. To 

 my mind, everything has colour — be it black, white, red, blue, etc. — 

 unless it is transparent and transmits all rays. It is only a matter of degree 

 after all. We begin with white which reflects everything, and pass on 

 to pale colours which absorb a few rays and reflect many, and so on ujj 

 to black which absorbs everything. We are not talking of light (of 

 course white light will split up into a rainbow of colours), but of white 

 paint, black paint, etc., and I have never heard any scientific man that I 

 have come across object to melanin being termed black pigment. On 

 the matter of Thecla rubi, I have nothing to say at present, but will 

 wait until I have had time to put it under the microscope by daylight. 

 With regard to refraction [? diffraction. — Ed.] and brightly coloured 

 insects, it must not be forgotten that a very great number, I may say 

 most, of the gorgeously coloured Papilios, Ornithopteras, etc., come from 

 the gloomy forests of South America and the Malay Archipelago. Now, 

 of one thing 1 am convinced, you cannot have pigment without sunshine, 

 e.g. deep sea molluscs, worms and cave reptiles, which are colourless 

 and transparent, blood pigment being always present, liowever, in the 

 reptiles ; therefore, I think, it is in these insects that some of the best 

 examples of colouring by refraction will be obtained. No one, I oj)iue, 

 will deny that the piirple of Thecla querctis and Apatura iris is refractive. 

 The green of Miselia oxyacanthae, which gives a reddish tinge when 

 the direction of the light is changed, appears to me to be of the same 

 character as that of Thecla rubi, and I think that in this insect the var. 

 capucina is ])robably the ancestral form. Can Mr. Tutt, or any one 

 acquainted with Continental insects, tell me if var. cajmcina is com- 

 moner in the north than the form usually considered typical ? I get 

 var, capucina here in the proportion of about 1 : 4, — 11. Fkeek, M.B. 

 Jan. 30th, 1896. 



