INTRODUCTION Jv 



the pronotum. In wing-development and in the setae the Hawaiian series are, as a 

 whole, remarkably deficient as compared with foreign forms. Three of the lo genera 

 in the division characterized by simple tarsi are fully winged and can fly, six have the 

 wings quite rudimentary, but in one of these, Barypristus, the one species {incendiarius) 

 has wings about twice the size of the other [j'ltpico/a), while one genus, Chalcomenus, 

 has large wings, only the apical portion being somewhat reduced. It is, however, 

 flightless, and no doubt represents an early stage in wing-degeneration. In the other 

 division one only (Colpocaccus) of the seven genera possesses functional wings, the 

 others having these organs quite rudimentary. The prothoracic chaetotaxy appears to 

 be in a more unstable condition than was supposed to be the case at the time this 

 character was utilized for generic distinction. Thus Barypristus incendiarius is now 

 known quite commonly to be devoid of any pronotal setae, or to have a seta developed 

 on one side only. Apteromesus macnlatus has sometimes a seta near the hind angles 

 of the pronotum. Mesothrisais vagans rarely develops a weak seta at the posterior 

 angles, so that certain examples might on this character be placed with the Hawaiian 

 Platynus. One example of a small batch of the very distinct Meiromenus fossipennis 

 was found to bear a well-developed seta on each side-margin of the pronotum near the 

 middle, so as to become a Mesothriscus. It is now known from the examination of 

 individuals taken in company, that some of the Pterostichine species also vary in the 

 setae, so that individuals of one would on this character be placed in two genera. 

 Apart from the variability in the chaetotaxy, it certainly appears to me that the use 

 of this character for generic separation tends to place in different genera species' that 

 are really closely allied. Excepting the Barypristus mentioned above and a few of the 

 Pterostichine Carabidae, it is proper to state that variation from the normal number of 

 setae is rare and exceptional. 



The occurrence of endemic Hawaiian species referred to a foreign genus, Platynus, 

 needs special notice. The two known species of this genus (apart from chaetotaxy) 

 are not closely allied to one another, but each much more closely resembles species 

 placed in other Hawaiian genera. If they truly belong to Platynus, then it would be 

 necessary, if we maintain the view that the Hawaiian Anchomenini have been derived 

 from a single immigrant form, either to consider this genus (since it is the only one 

 known outside the islands) as having given rise to the other endemic forms, or to 

 suppose that Platynus has arisen independently in the Hawaiian group. The Hawaiian 

 Platynus is not central in the series of Hawaiian genera, this position being held by 

 such forms as Colpocaccus and Mysticomenus, both of which it may be noted are fully- 

 winged forms. It should have been noted above that these fully- winged forms are 

 very poor performers on the wing. I think it probable that the Hawaiian Platyni will 

 ultimately be found to be more closely allied to other of the endemic Anchomenini, 

 than to foreign Platynus, and will be separated from the latter. 



' Some of these species are not only extremely similar in structure apart from the chaetotaxy, but 

 have peculiar and identical habits. 



