STONE-FLIES. 



STENOPERLA PRASINA. 



Chloropcrla prasina, Newman, Zoologist, vol. 3, 

 p. 852 (1845). Hermes prasinus, Walker, Cat. Neuroptera 

 Brit. Mns., p. 206 (1852). Stenoperla prasina, McLachian, 

 Trans. Ent. Soc, ser. 3, vol. 5, p. 354 (1866). 



(Plate I., fig. 4, fig. 5 larva, enlarged.) 



This pretty insect is fairly common throughout the 

 whole of New Zealand. 



The expansion of the wings varies from 1^ to '2^ inches. The insect's 

 general colour is grass-green, with the metathorax and abdomen brown. 

 The head is hardly broader than the prothorax, the latter being rounded 

 behind. The rest of the body is very narrow. The fore-wings are narrow 

 and bright green, especially in the living insect. The hind-wings are very 

 broad and pale green. The legs are also green. 



The larva of this insect is found in rapid-running 

 rivers and streams, but apparently is not usually very 

 abundant. It is extremely active in the water, and gene- 

 rally contrives to secrete itself under a stone immediately 

 after being exposed to view. Thus it is always very 

 difficult to capture, which circumstance perhaps gives 

 rise to an idea, that the larva is less abundant than is 

 actually the case. The food of this larva consists of 

 various other aquatic insects, chiefly the larvae of 

 Ephemeridce, those belonging to the genus Atalophlebia 

 being probably the favourite prey of this insect. It also 

 •devours the larva of Ameletus perscitus. The larva of 

 S. prasina actively pursues its victims amongst the stones 

 in the bed of the stream, and seizes them by means of 

 its powerful jaws. It is extremely voracious, and might 

 perhaps prove destructive to very young trout. On the 

 other hand, there is no doubt that these larvae must in 

 turn form an important element in the food supply of the 

 trout themselves, as the insects are to be found in the 

 streams throughout the entire year, being, in fact, as 

 common in midwinter as at any other season. 



The length of the full-grown larva, including the terminal appendages, is 

 about 1^ inches. In general appearance it bears a considerable resemblance 

 to the perfect insect, except, of course, in the matter of wings. The head 

 and thorax are dull brownish-green ; the former has three conspicuous 

 hlack spots on the top, representing the ocelli of the perfect insect. The 

 meso- and meta-thorax are each furnished with a pair of wing-pads. The 

 anterior pair are very vivid green in colour, the posterior pair being paler. 

 The abdomen is purplish-brown with the segmental divisions sharply marked 

 in white. The first five segments of the abdomen are each furnished with 

 n pair of gills, one gill on each side. These appendages are cylindrical, and 



