27 6 THE BRITISH NATURALIST. [December 



the pond or water-plant to which it is anchored by the suction-like action 

 of the false feet, and thus acting as buffers, to allow the rotatory tufts 

 free play in the water, especially if there should be a slight ripple 

 thereon. 



I now come to the point where I am certain both Stceger and Meinert 

 are in error. At all events the remarkable difference between their 

 observations and descriptions and those of De Geer and De Reaumur, 

 fully confirmed by myself after long and caref ul observation and experi- 

 ment, would lead one to think that the habi ts of Dixa nigra which 

 Stoeger examined differ radically in one respe ct from our species, which 

 I think will probably turn out to be Dixa amphibia. Translating from 

 his French resume, Meinert says " The larva holds on by its false feet 

 and its rows of bristles fixed to the upper parts of the plants rising 

 above the water, but having its head and the extremity of its 

 abdomen resting on the water in some such curved position as is 

 represented in figure 103." Now I could have understood this exactly 

 if the figure 103 had been drawn so, f\ ; but in the plate the Dixa is shown 

 with the body hanging down so, (J ; and this agrees with Stceger's 

 statement in Danish, viz., " Lying on its back it is firmly attached to 

 the water-surface by means of the suctorial organs of the tail and the 

 pair of suction valves (false feet) in such a manner that the part of the 

 body being in between will hang downwards in the form of an arc." 



All I can say is that this -was not so in any of the specimens I have 

 examined — the animal always withdrew its body clear from the w r ater, 

 the bend going first, so graphically described by De Reaumur. I tried 

 the experiment of withdrawing the piece of valisneria to which the 

 larva was adhering, and quickly replacing it in the water with the body 

 downwards ; it always immediately moved itself round until its head 

 and tail once more touched the water, with the body out, though 

 surrounded by plenty of moisture. 



The tail of the Dixa larva deserves our next attention, for it is a 

 very complex organ, differing largely from all other Dipterous larvae, 

 but presenting resemblances to the pupa of Chironomus and other 

 Diptera, especially in their hairy tail-plates, and, as Mr. Hammond, 

 says, "this fact is curious and suggestive." The tail is affixed to 

 the nth segment, and at its origin it has on each side a small brown 

 papilla armed with bristles ; next there two lobes or elongated 

 protuberances, directed outwards, and bordered with bristles of the 

 same length, as if cut with scissors. These horny fringed plates serve 

 as floats to enable the larva to keep its tail on the surface, and not to 

 allow the pair of stigmata to be submerged when the water is ruffled. 

 The latter are well shown in the tail enlargement in Plate XI. These 

 " suctorial organs," as Stoeger calls these spiracles, are crescentic in 

 shape, and are used partly as feet, possessing similar hooklets to the 



