1 FAUNA HAWAIIENSIS 



fully developed. It is not quite certain whether winged and flightless forms may 

 not occur even in the same species in one instance. 



In the Elateridae of the subfamily Eucneminae, an uncertain number of the 

 species of Droviaeolus are flightless, while many of the genus are fully winged and 

 are occasionally taken in the act of flying. Of the true Elateridae Dr Sharp believes 

 that one form, Dacnitus cufrax, is flightless. It is allied to the endemic genus 

 Itodacnus, which flies freely. 



The single Lucanid genus Apterocyclus, somewhat allied to Dorcus, is flightless 

 and endemic. 



The Nitidulidae are mostly fully winged, but four genera, containing in all nine 

 species, are flightless, while the remaining 1 29 species in nine genera are fully endowed 

 with flight. The amount of degradation of the wings in the flightless forms varies 

 according to the genus or species. 



The endemic Histeridae of the genus Acritus have flightless species, but these 

 are probably much less numerous than the fully-winged ones. 



In the Staphylinidae some of the species of Myllaena are apterous, their congeners 

 being fully winged. 



Of the endemic Carabidae 184 are flightless, the fully-winged species only 20. 

 Nearly all the flightless endemic insects are inhabitants of the forest, or if they 

 frequent exposed situations like some of the Carabidae, they are closely related to 

 species that frequent thick forests and are equally flightless. There is no ground 

 for supposing that in these islands, as has been suggested for flightless insects in- 

 habiting other Oceanic islands, the wings have been lost or degenerated through 

 the agency of natural selection, as being a source of danger, if used on small land 

 areas, where flying insects are supposed to be liable to destruction from being blown 

 out to sea. Only in the case of the moth, Hodegia apatela, could this theory be applied 

 by any stress of imagination. So far, Hodegia is at present only known from open 

 and wind-swept localities, and it inhabits these both above and below the forest 

 region. Practically it is a flightless species of Thyrcopa, and fully-winged examples 

 of this genus have been observed to flourish in the most wind-swept of all regions 

 close to the sea margin. Still more delicate Microlepidoptera are found in similar 

 open country, and many of these as well as the fully-winged species of Tliyi-copa 

 seem to be far more successful than the Hodegia. 



All the cases of flightlessness in Hawaiian insects are, I believe, to be explained 

 simply by ' disuse.' 



If we consider the case of the endemic Heteropterous bugs, we find that all the 

 flightless forms are either entirely or to a great extent of terrestrial habits. The 

 winged species of Metrarga though they may descend to the ground, yet habitually 

 breed on certain plants, often at a height from the ground, but the terrestrial 

 M. villosa is flightless. All the truly arboreal Reduvioli are winged and are 



