IC)14] F- H Gravf.ly : -4;/ Account of the Oriental Passalidac. 263 



the Bulutota specimens indicate with sufficient clearness that a larger series would 

 prove the range of variation to be perfectly continuous, as it is in the other four 

 variable forms ; for which reason I have described them above without the introduction 

 of any new name. This view, as will be seen later, is further supported by the fact 

 that Episphenus comptoni is a gregarious species, is the only asymmetrical member 

 of the Aceraiinae found in Ceylon, and is also the commonest member of that sub- 

 family living in the island . 



The specimens from which my descriptions of Episphenus indiciis and Acerains 

 grandis sub-sp. hirsiitus were drawn up show, as a whole, no breaks in the continuity 

 of the range of variation in length. Moreover they seem to indicate that different 

 colonies differ from one another in average size, and that the lengths of different 

 members of any one colony do not usually differ very greatly one from another. 

 The evidence is most definite in the case of Aceraius graniis. Out of a series of 

 38 specimens of this species known to have been taken from a single colony at 

 Janakmukh, 37 show a continuous range of length from 36 to 39 mm., the remain- 

 ing specimen being 33 mm. long ; and again, the specimens from Kalek form a single 

 short series of individuals all between 38 and 40 mm. in length. On the other hand, 

 two specimens, presumably of opposite sex, taken from a single burrow at Rotung 

 were 34 and 41 mm. long respectively. Such facts suggest that although large and 

 small specimens may be quite well able to unite to found a new colony, their off- 

 spring tend to be to of a moderately uniform size ; and that the majority of speci- 

 mens in each colony are the descendants of the original founders of that colony, 

 which do not leave their home until they are compelled to do so, when they may 

 either found new colonies or enter the ranks of an old one from whose average size 

 they may differ very considerably. 



Such evidence as is available regarding the variable species of lyCptaulacinae all 

 points in the same direction. Leptaulax dentatus, s. str., is represented in our collection 

 by over three hundred specimens, whose range of variation in length is unbroken; 

 but when these are arranged according the localities from which they come, it is found 

 that those from each well-represented locality fall into several separate series, each of 

 which probably includes only specimens from colonies that are not represented in 

 any of the other groups, unless it be by one or two specimens that have come into the 

 colony from outside. I have not attempted to make any elaborate measurements 

 with which to support these facts ; for length measurements of dried Passalids are 

 only approximately comparable one with another, on account of the variable extent 

 to which the back of the head and front of the metathorax are telescoped into the 

 prothorax ; and breadth measurements are so variable in proportion to length that 

 it would be still more misleading if I were to use them as an index of length. The 

 following measurements of the extreme members of each of the several unbroken 

 series, into which the specimens from each of our three best represented localities 

 appear to the unaided eye to fall, will I think give a better idea than anything else 



I Since the above was written I have obtained direct confirmation of the continuity of the variation 

 found in this species. See below, p. 282, footnote. 



