INTRODUCTION ccxxv 



be fixed. It is quite certain that a very large number of the forms, that have been 

 described as distinct, are not true species in the same sense that the majority of the 

 species of insects are. On the whole the phenomena of variation in Achatinella are 

 rather different from those exhibited by the variable forms of insects, but these are 

 probably explicable by the very stationary habits of the Mollusca, and the difference 

 between the two groups is rather of degree than of kind. On the other hand, I think 

 it probable that a good many of the forms of Achatinella, which differ very little in 

 appearance or structure, are absolutely distinct species. In this they are quite paralleled 

 by many insects, for we know that in these, perfectly distinct species are sometimes 

 separated by characters apparently much smaller than those exhibited by the extreme 

 varieties of other species. There are numerous cases in insects where one particular 

 variety of a very variable species has its peculiarities exactly reproduced as a constant 

 specific character of an allied species, and I have found, as I interpret the species, 

 exactly similar cases in Achatinella. But in the insects the complexity of structure 

 allows us to be certain of the real specific distinctness of such forms, owing to structural 

 differences that exist to confirm it, whereas the Mollusca (at least as studied from the 

 shells) are very poorly endowed with structural characters, on which to base specific 

 distinctions, as compared with even the most simple form of insect, and one is obliged 

 to place more or less faith in colours and patterns of colour. In many groups of 

 Hawaiian insects such characters, if relied on for discriminating species, would lead to 

 hopeless confusion. 



It has always been a tradition with the natives that the Achatinellas are able to 

 sing or produce musical sounds, but I know of no confirmation of this excepting the often- 

 quoted observation by Barnacle. Though I have lived for weeks in spots where shells 

 were to be found on the trees immediately surrounding my camp, I have never heard 

 any such sounds. So confirmed were the natives in their opinion, that the song of the 

 land-shells was even put to words. An old native, whom I once had with me in the 

 mountains of Oahu, one night called my attention to the song of a land-shell, but I 

 actually found the creature, a species of small cricket {Paratrigonidium) that was 

 making the sounds. Though the motions of the elytra in producing its song were 

 quite visible, he utterly declined to believe that it was caused by the cricket, and 

 persisted that it was due to a land-shell. I would suggest that what Mr Barnacle 

 heard (making allowance for an exaggeration in description) was the stridulation of 

 crickets beneath the bark of a tree, where they often congregate, and what he saw was 

 a group of Achatinella on the bark. Several natives have informed me that the real 

 singing shells were found especially on the ' Ki' plant [Cordyline), and it is certainly 

 curious that this same plant is a favourite home of the larger green crickets of the 

 genus Banza. 



The bright coloration of the Achatinellas, especially of many of the banded forms, 

 is of some interest, because it reminds one so strongly of many other animals, in which 

 a somewhat similar strong contrast of colours is supposed to produce the effect of 

 F. H. I. ff 



