50 



n Selection from tDe £ectures and 

 Papers Qiuen before the Societp, 



Contributions to a Theory of Beetle Colouration:; 



Abstract of a Paper by 

 Joseph Neale, B.A. 



(Read before the Zoological Section, November 6, 1918.) 



rno any one general statement of a theory of colouration there 

 are so many exceptions that the theory may appear to be 

 discredited unless it is remembered that cross-currents of tendency 

 require careful analysis before the broader features are detected,, 

 and that the protection due to colour is a relative rather than, 

 an absolute immunity. 



Subject to this introductory caution, it may be stated that 

 all colour is purposeful and the following generalisations show 

 the correlation of the habits and colours of beetles : — 



1. Beetles of habits mainly nocturnal or crepuscular — 



that lie hidden in the daytime — are chiefly black or 

 dusky. 



2. Beetles of diurnal habit are coloured : 



((a) in mottled or broken shades which assimi- 

 late them to their surroundings, or 



(b) in colours more or less conspicuous, render- 

 ing the insects easily visible. 



Of (b) are all the " carnivorous ground beetles " many of 

 which, though black as befits their nocturnal habit, are shiny and: 

 readily seen in daylight, while those chiefly diurnal, as the " sun- 

 shiners " to be seen on our roads and paths in spring, glitter in 

 metallic sheen of bronze or copper, or in variegated black and 

 red, black and yellow, or black, red and yellow, in glaring contrast. 



" Carnivorous water beetles " are dull olive brown for con- 

 cealment, or in chequers or stripes of black and red or yellow. 

 The great Dytiscus is olive green above but with a warning 

 border and underside of yellow, which are conspicuous as it rises 

 to the surface to breathe. " Cocktails " such as the Devil's 

 Coach-horse and its allies, another family of flesh and carrioni 

 feeders, are, if diurnal, in warning colours of black and red. 



