IM)LL\ DRAaONFLIES. 469 



Tho Zygoptoridto Larvjw. 



Theso larviu agroo in their (.-Dinposito parts with those of tho Anisopteridse 

 with tho singlo exception of tho respiratory organs situated at the anal end 

 of the abdomen but the shape of the various parts differs considerably. 



The head is on a much smaller scale (Plato X, ligs. 2 and o), tho eyes much 

 further apart and in the genus Micromerus, distinctly conical and broadly 

 rmmied. The ocelli stand out much more distinctly as three reniform 

 bodies, the convexities of which are opposed to each other. The whole insect 

 is more diaphanous and its internal anatomy thereby niore apparent. This 

 applies especially to the head in which many interesting structures may be 

 seen, thus two large ganglia, centrally placed, are conspicuous objects from 

 which run branching root-like nerves forward to the antonme, the "olfactory 

 nerves," and thick cord-like nerves outward to the eyes, the " optic nerves," 

 and lastly two nerve tracts backwards which after traversing the prothorax 

 and thorax, pass back into the abdomen connecting up with a chain of 

 ganglia. 



The masiv of tho labium is more simple than in the Anisopteridie : in the 

 Agrioniues the jaws are furnished with a simple bifid tooth and the anterior 

 border of the end plate is prolonged forward into a triangular projection 

 furnished with minute points. In the Ilhinocyphiute, the mask is very 

 much the same but the jaws themselves are bifid at the end, each arm being 

 furnished with a bifid tooth and there is no projecting anterior border to 

 the end plate. The masks of the Zygopteridse are never cupped but lie 

 thit, covering in the mouth parts below the head. 



The 2)rothora.v is vawah. smaXlev than that of the Anisopteridse and does 

 not vary very much from that of the imago, its division from the thorax 

 being more sharply defined. 



The thora.c is longer and narrower and the wing-cases long, narrow 

 and cylindrical and strongly keeled on the dorsum, their shape being 

 very similar to those of the Gomphines. The whole larva is much 

 more attenuated and a more mobile and lithe creature than the 

 larvte of the Anisopteridix;. The action of the latter is jerky and their 

 progress made by leaps and bounds whilst the movements of Z3'gop- 

 teridoe are more smooth, continuous and lissome like that of a fish or sea- 

 snake, the whole abdomen being brought into play and lashed from side to 

 side as they pass through the water. This action is materially helped by 

 tho anal appendages which are found in these species and which form an 

 important part of the respiratory system. In the Agrionines, these are, 

 three, stalked, lamellar-liko structures which are shaped differently in the 

 species. Attached advantageously to the hinder end of the abdomen, 

 they perform a secondary function as a propelling organ, serving in 

 the same way as the tail of a lish. The proximal half of these 

 organs is a stalk, through which runs the bronchial tube, the distal 

 part being translucent and containing between its layers the branchiae 

 which here break up into root-like masses, the extremities of which end 

 in minute, pigmented papilke. Air is absorbed through these latter and 

 finds its way through the bronchi, which run througli the ctclomic cavity 

 and so ultimately to the trachto by which it is distributed to the different 

 parts of the body. Removal of the respiratory lamelke does not result 

 ni the death of the larvse as would be expected, so that it is evident that 

 these do not form the only organs of respiration. Very probably the 

 rectum is also used in the same way as found in the Anisopteridie. In the 

 llhinocyphinto, the place of these lamellte is taken by two long, tapering 

 tubes which are nearly the length of the abdomen. The Eupha3a are said 

 to respire by a system of spiracles situated on the abdominal segments, 

 but this and many other points in regard to the working of the various 

 systems of respiration require further iTivestigation ; especiallj- are we in 



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