COLEOPTERA 179 



it has, I believe, been stated that the insects of islands Hy either better or worse (in 

 many cases not at all) than those of continents. The former of these alternatives can 

 scarcely be true as regards the Hawaiian Carabidae. Several of the species that have 

 powers of flight have so limited a distribution within their haunts that it is clear they 

 avail themselves of their wings very little ; Colpocaccus. one of the winged genera, is 

 more numerous in individuals than most of the other Anchomenides, but it is a feeble 

 form, and doubtless — like most other beetles — drifts rather than flies. 1 do not think 

 that the factors that have induced loss of wings in Hawaiian Carabidae are at all well 

 expressed by Darwin's formula. I look on the loss of wings as induced probably by 

 changes of habit becoming correlative with modes of growth ' : and though the results 

 may be effected to some extent by disuse, I think they have been mainly controlled by 

 changes in habits, in instinct, and in physiological processes resulting from those prior 

 modifications, and again inducing changes in the correlation of various parts of the 

 body. Whether selection has played any part in the matter is clearly uncertain. 



Vestigial wings. It is commonly supposed and frequently stated that flightless 

 or wingless beetles are apterous. This is a complete mistake, nearly the whole of the 

 species called apterous really possess four wings ; the anterior pair being transformed 

 into elytra and the posterior pair reduced to appendages of varying size and form 

 according to species, genus, etc. That these appendages are vestiges of organs that 

 were formerly larger and then functionally useful is, for a variety of reasons that cannot 

 here be discussed, probably true in a majority of cases if not in all. At the same time 

 this does not prevent it from being also true that they may in some cases be rudiments 

 as well as vestiges ; in the sense that they may become again increased after having 

 underpfone reduction. These vesticrial organs have been examined bv me in the 

 Hawaiian Carabidae to a certain extent, and I have made use of them for the purpose 

 of establishing genera. I have invariably treated a species in which the wings are 

 capable of being used for flight as of a different genus from one in which they are 

 useless for this purpose. A functional wing is, in Carabidae, in the condition of repose 

 twice folded ; once by being bent (not doubled, but turned as if hinged) just proximal 

 to the stigma on the costa, and again quite near to the tip. The functionless wings, or 

 vestiges, are never thus folded even when they are of their largest size ; their nervura- 

 tion is very much reduced, and the apical part of the wing — that part beyond the 

 stigma — is in Hawaiian flightless forms completely absent. There is in fact a great gap 

 structurally between the functional and the functionless wing. 



On the other hand the functionless — or vestigial — wing differs greatly according to 

 species, as will be seen by reference to our plates. 



Although great interest attaches to these vestigial wings of Coleoptera they have 

 been very litde studied, and I think therefore it will be worth w^hile for me to set forth 



' The bionomical notes at the conclusion of this memoir are of special interest in connection with this 

 subject. 



