NEUROPTERA 63 



AGRIONINA. 

 Agrion Fabr. 



The dragon-flies of the genus Agrion are amongst the most important repre- 

 sentatives of the Order of Neuroptera in the Hawaiian Islands. Several species are 

 found on all the more important islands of the group, and the range of many of them 

 extends over several islands ; wherein they differ from the greater part of the endemic 

 insects, which are for the most part confined to a single island ; or to one or two 

 of those which lie most closely together. At the same time, when a series of examples 

 of a species from different islands is compared, certain more or less constant differences 

 are often observable, especially as regards size. 



Perhaps the most interesting facts relate to the earlier stages, or nymphs, which 

 are aquatic and carnivorous. Excluding these dragon-flies and a few water-beetles, 

 the insect fauna of the streams and pools is almost non-existent. The Ephemeridae, 

 Perlidae, and Trichoptera, usually so numerous, are entirely unrepresented in the 

 Islands, although the mountain streams, rising at high altitudes, with their superb 

 waterfalls, and various temperatures, appear admirably adapted for many of these. 

 It is therefore not a little surprising to find the group of dragon-flies so well represented, 

 and that the individuals are so numerous, being on the whole the most conspicuous 

 of all the endemic insects. In the absence of the groups above mentioned, I believe 

 that their main food-supply comes from without, consisting of such creatures as 

 accidentally fall into the water. Under ordinary circumstances this is not great, but 

 after rain, when the streams rise very quickly, food becomes abundant. When the 

 streams, as is often the case, become nearly dry, large numbers of creatures resort to 

 the pools that are left, for the sake of the moisture, and the numbers that come to grief is 

 often astonishing, the whole surface being covered with the drowned and drowning. 



There are, however, other species, the nymphs of which live under very different 

 circumstances. These have given up their aquatic life, and live hidden at the bases 

 of the leaves of a liliaceous plant — Asteiia veratroides. Sometimes a little water 

 is held by the plant around the stem, but more often there is merely a collection 

 of damp earth and dead leaves. These nymphs would even appear to dislike the 

 collections of water, for in wet weather they often crawl half-way up the leaves, instead 

 of remaining at the base, where the water accumulates. They differ in some points 

 from those which frequent the water ; they are shorter and stouter, and much more 

 sluggish, and the caudal appendages are very short and thick, differing therein 

 greatly from some of the aquatic species, the appendages of which form beautiful 

 tracheal gills. 



On the whole they are without doubt better off as regards a food supply than 

 the aquatic species, for there is generally abundance of animal life around them. 

 F. H. II. 9 



