xlviii FAUNA HAWAIIENSIS 



ant-lion {For7nicaleo) — insects which could only have arrived on their wings — have 

 been able to traverse a similar expanse of ocean by some rare chance. In many 

 cases the winged insects may not have arrived this way, because in their earlier 

 stages they could well have been carried like the flightless beetles and wingless 

 animals. Over what distance minute and delicate winged insects can be wind-borne 

 is not known, but probably under favourable circumstances it is very great. Some 

 small moths, as reported by Muir and Kershaw, are able to rest on the sea and 

 again take wing, but such cases are probably rare, and I imagine this faculty would 

 not be of much aid in traversing such great distances as we require. High and 

 steady currents of air are probably most efficient. A number of the existing species 

 of moths are of powerful flight and are partial to wind-swept country, and it is a 

 familiar sight to see these, when disturbed, allow themselves to be carried far away 

 on the strong wind. Given this habit of allowing themselves to be thus carried, 

 small moths might even be able to pass over greater distances than heavier-bodied 

 species. In the interisland distribution of species whirlwinds may have occasionally 

 assisted. These are most frequently observed on the plains, and I have recorded 

 how even so strong a bird as the imported Acridotheres may be carried up many 

 yards before it can extricate itself. These whirlwinds have been seen to carry up 

 thick columns of dust to an elevation of over 2000 ft., and we have once or twice 

 observed them to originate at this elevation in the mountains. Small creatures 

 carried up in this way and meeting high currents of air might be borne for great 

 distances before alighting. 



Flightlessness in Hawaiian insects. 



Amongst the Hawaiian insects there is a very large number of species in which 

 either one or both pairs of wings are so reduced as to be useless for purposes of flight, 

 or the hindwings may be entirely wanting. These cases in which we may suppose 

 the loss of the powers of flight to have originated within the islands themselves 

 are of considerable interest, and we may briefly review the insect fauna from this 

 point of view. 



In Lepidoptera one case of flightlessness only has been so far observed, that 

 of the large Gelechiid moth, Hodegia apatela, the female of which has all the wings 

 so reduced as to be quite useless for flight. The male is not known, but it is very 

 probably fully-winged. This genus is merely an offshoot of the endemic fully-winged 

 and dominant genus Thyrcopa. 



In Diptera, flighdess forms are, so far as is known, confined to the Dolichopodidae, 

 several species (probably of two genera) having these organs reduced to mere filaments. 

 One of these, Emperoptera, is an active and brightly metallic little fly, living on the 



