264 Memoirs of the Indian Museum. [Voi,. Ill, 



of what has been found. Out of 46 specimens labelled " Upper Tenasserim " 17 are 

 21 ■5-24-5 mm, long ; 2 are 26*5 and 28 mm. long respectively ; and 27 are 30-37 mm. 

 long. Out of 45 specimens labelled ''Tenasserim" 21 are 21-24-5 mm. long, i is 

 27-5 mm. long; and 23 are 30-35 mm. long. And out of 43 specimens labelled 

 "Sikkim" 2 are 19-5 and 20 mm. long respectively, 8 are 21-23 mm. long, and 33 are 

 24-5-31 mm. long. On the other hand, 47 specimens known to have been collected 

 from a single- colony at Kawkareik are all 29-33-5 mm. long, and form a single 

 unbroken series. 



Leptaulacides hicolor is unusually variable in the extent to which the body is 

 flattened, as well as in total length, and in the extent to which certain plates are 

 punctured. For this reason, and partly, perhaps, because the specimens I have seen 

 belong in almost equal numbers to two different forms of the species, which must, at 

 least provisionally, be treated separately, these specimens have proved not to be nearly 

 enough to form a satisfactory basis for any full account of the manner in which different 

 colonies vary one from another. It appears, however, that size is not a character 

 that is at all likely to prove of any great importance for the sub-division of the 

 species into sub-species or varieties. 



Members of a single colony in this, as in other variable species, probably differ 

 comparatively little one from another in size, which suggests that the}^ may be com- 

 paratively uniform in structure also. Any investigations on a collection in which 

 different individuals, instead of different colonies, have to be taken as units, must be 

 conducted with great caution ; for the presence in collections of a number of short 

 series from different colonies, is likely give a false appearance of the constancy of a 

 number of more or less distinct types ; and I am confident that this fact more than 

 any other has led, on account of the remarkable variability of the common species 

 L. hicolor and L. dentatus, to the appalling multiplication of so-called species of the 

 genus Leptaulax. The colony ought, in my opinion, to replace the individual as the 

 unit for taxonomic work in all these variable species, and it is partly in the hope that 

 collectors will turn their attention to collecting separate colonies, and partly to avoid 

 adding to what I am convinced is largely a meaningless multiplication of names, that 

 I put forward here, on the somewhat inconclusive evidence at present before me, the 

 hypothesis that members of any one Passalid colony are much more uniform than 

 the species as a whole when this is markedly variable. 



In connection with this hypothesis it would be interesting to know how long logs 

 of different kinds can remain suitable for the habitation of a single species of Passalid 

 under the normal conditions of different jungles, and the length of time occupied by 

 the life cycle of different species of Passalidae in various localities, together with any 

 facts relating to the period or periods of reproduction of individual pairs. For if logs 

 rot more rapidly than colonies can be formed, it would follow that colonies are 

 produced by the attraction of suitable food ; in which case the members of each would 

 be unlikely to have a common descent, and it would no longer seem so probable that 

 members of a single colony should be more uniform than the species to which it 

 belongs. 



