BY E. J. TILLYAKD. 417 



making an angle of from 45° to 60° with one another. The 

 medial gill-plate stands up between them at an angle of about 

 75° to the horizontal. In shape they are irregular, elongate, 

 suboval; the medial one being slightly shorter and somewhat 

 broader than the lateral ones. The main longitudinal trachea 

 runs the whole length of each gill-plate, dividing it into two 

 unequal portions; in the medial, the narrow portion is uppermost; 

 in the lateral, it is underneath. This main trachea carries on 

 either side from 40-50 branches or secondary tracheae, these being 

 slightly more numerous in the medial than in the lateral plates. A 

 few of these are themselves bifurcate or possibly even trifurcate. 

 These secondary trachea? are all practically at right angles to the 

 main trachea, this being characteristic of all the Lestes nymphs I 

 have examined. In other Agrionid genera such as Ischmora and 

 Pseudagrion the secondary trachea? run oblique to the main one. 

 Colour, a bright transparent brown; main tracheae dark brown. 

 Generally the plate is crossed by three irregular broad bands of 

 suffused rich dark brown, as shown in the figures. Edges 

 minutely and densely serrate, the serration not being visible to 

 the naked eye. Altogether these plates are most beautiful objects 

 for examination under a magnification of from 10 to 20 diameters. 



The above description applies to a well coloured larva-nymph, 

 and is probably the commonest type. However, the colouration 

 varies greatly, some specimens being almost without markings of 

 any sort and of a complete beautiful pale transparent green. 

 Others are but slightly marked, and others again are even darker 

 than the one described. As for the gill-plates, these may be pale 

 transparent brownish or greenish (this very rarely) with no 

 bands; or they may be slightly suffused with pale brown bands; 

 or frequently the bands are so broad and dense as to be almost 

 black and cover nearly the whole surface. In one or two speci- 

 mens I have found them a bright salmon-pink colour. This varia- 

 tion in colour does not seem to be due to locality, all forms 

 described having been taken in one small water-hole. 



The larva-nymph is distinguished from that of allied species as 

 follows : — That of L. analis, so far as I have been able to get any, 



