a 



Vol. X, No. 6.] Indo- Australian Passalid Coleoptera. '03 



equally abundant and widely distributed. But one of them 

 (Episphenus 1 indicus) is much more variable in size than the 

 other (E. neelgherriensis), and usually much larger; it also 

 appears to be slightly gregarious and the other not * ; and besides 

 having, if anything, slightly more highly asymmetrical man- 

 dibles than the other, it differs from it in having the anterior 

 angles of the head produced forwards, a character found in 

 few species of the genus Aceraius, and in an especially pro- 

 nounced form in the dominant species of that genus. 



In Ceylon the parallel is even closer. The dominant and 

 only asymmetrical species {Episphenus comptoni), which is again 

 of much more variable, and usually of larger, dimensions than 

 the other (E. moorei), is far more abundant. It is also 

 markedly gregarious. Nothing definite is known about the 

 habits of the other species ; but it is sufficiently evident, from 

 the absence from collections of any considerable series from a 

 single locality, that specimens do not live together in large 

 numbers. With regard to distribution, the data are probably 

 insufficient for any generalization as regards either species. 



I have not been able to study the Gnaphalocneminae in 

 such detail as the Aceraiinae: but it is already evident that 

 they present phenomena of at least a similar nature. Thus in 

 the Gnaphalocnemis group— the only group of the subfamily 

 that has established itself in the Oriental Region— species be- 

 longing to the genus Gnaphalocnemis are moie numerous, are 

 much better represented in collections, and attain a much 

 larger size than those of the less markedly asymmetrical genera 

 1 rapezochilus and Parapelopides; and the symmetrical or almost 

 symmetrica! genus Parapelopides is the rarest of the three, 

 similarly in the Gonatas group also, species of the genus 

 Gonatas are more numerous, larger, and better represented in 

 collections than those of the genus Omegarius. 



Another point which is brought out in pi. XXI V is the way 

 in which the degrees of asymmetry, severally attained by 

 the three dominant species of Aceraiinae, are related to the 

 distribution of these species. Thus Episphenus comptoni in 

 Oeylon is less highly asymmetrical than E. indicus in the Indian 

 peninsula; and E. indicus is itself less highly asymmetrical 

 than Aceraius grandis on he other side of the Gangetic Plain. 

 I he dentition of even the dominant Indian Peninsula form 

 is, indeed, less highly asymmetrical than that of the great 

 majority of the species found beyond the Ganges ; and both 

 the Peninsular forms are more highly asymmetrical than 



in ,„ Incl * Chilomazus (part) 4- Basilianus (part), see Mem. Lad. Iks. 

 "I, 1913-1914, pp. 316-8. 



1 both species, of course, the two parents live together with their 



aryai offspring, as is usual in the Passalidae. Gregariousness, as here 

 ncterstood, implies the association together of several such families. 



