

clxxviii FAUNA HAWAIIENSIS 



Hitherto no dark-bodied form of the male of any of these species has occurred, 

 all being largely red, nor has any red-bodied female of A. heterogamias (which is 

 peculiar to Kauai) been found. Thus, it may be said that the females of A. oceanicum 

 and A. blackburni are dimorphic, whereas the female of A. heterogamias, so far as is 

 known, is not. Consequently A. heterogamias always exhibits striking sexual dimor- 

 phism. A. oceanicum and A. blackburni do so, when we consider the dark-bodied form 

 of their females ; but when we compare the red-bodied form of this sex with the other, 

 the sexual dimorphism in the latter two species is much less marked. In other countries, 

 Agrionids, the males of which are red-bodied, exhibit similar dimorphism in the females. 

 Cases wherein black-bodied species are dimorphic, having a red-bodied' form in the 

 male sex, are very rare, and I do not feel sure of having met with such, except in the 

 case of A. amaurodytum, and but rarely in that species. 



Extensive melanochroism of the (normally) largely red-bodied male of Agrion 

 deceptor is common locally, and other species are affected less frequently, and in a 

 lesser degree. 



Only the very driest coastal regions of the islands and the highest elevations in 

 the mountains above the region of streams and forest are devoid of any species of 

 Agrion. A. xanthomelas is a common insect in Honolulu gardens and in lowland 

 districts generally, not usually partial to the mountains, though in the Kona district of 

 Hawaii it is common about stagnant pools up to an elevation of about 3000 ft. It 

 is very numerous in individuals under conditions totally changed from the natural; 

 perhaps it now finds more numerous breeding places, and a more abundant prey in 

 the numerous insects that have been introduced by man in the region it frequents. 

 A. hawaiiense, another small species, is more local than the preceding, but also seems 

 to generally breed in stagnant water. Where it frequents streams, like that of the 

 lao valley on Maui, we have noticed that its chief haunts are quiet small pools, often 

 cut off, or at a distance, from the main stream. It also breeds numerously in upland 

 ponds of considerable size, where these occur. A. deceptor, viicrophya, and nigro- 

 hamatu7n also sometimes breed in stagnant pools of water, but more often in the 

 streams themselves, or at least in pools left standing in the beds of streams, when 

 these cease to flow. Most of the other species breed usually in running water, but on 

 one occasion we found the nymphs of the large A. heterogamias" numerous amongst 

 dead decaying leaves lying on the ground, and saturated with the wetness oozing from 

 a perpendicular bank, at the foot of which they lay. There was no standing water, 

 and the spot was at some distance from a river, and had no connection with this. From 

 this the transition of habits is not very great to what may be considered the true 

 terrestrial, or one might in some cases say, arboreal species. These {A. koelense, 



Teneral or immature examples, which instead of having a black or metallic-black abdomen, have 

 this of dirty red or pitchy colour, are not to be confused with truly red-bodied examples. 



^ The nymphs of the allied A. oceanicum are sometimes found in the wet moss on rocks in stream- 

 beds, and the young ones are preyed upon by the larvae of Rhatttus pacificus. 



