1911.] 250 



shorn. Oil the anal segment is a very peculiar structure (fig. 2) — a pair 

 of decurved spines or spurs, and at the base of each is a spiracle. The 

 use of these singular appendages is xery interest oil;', as stated in Prof. 

 Miall's "Natural History of Aquatic Insects," p. 94, in his remarks on 

 the larva of Donatio,, which is very similar in habits and structure to 

 that of Hdemonia : — " Roots of Nympluea frequented by Donacia were 

 observed by Schmidt-Schwedt* to exhibit peculiar scars. These were 

 'liscovered with difficulty, owing to the dark colour and uneven surface 

 of the roots. There was in each rase a rough hole, made apparently by 

 the jaws of the larva when feeding, and. at a distance corresponding with 

 the length of the body, a pair <>f small slits. On microscopic examination, 

 these slits were found to penetrate the epidermis of the roots. Some- 

 thing of this had been previously observed by Siebold, who in 1859 

 described the larva as biting a hole in the roots of Sparganivm, pass- 

 ing the end of the abdomen into it, pressing the spiracles by the help 

 of the curved spines close against the hole, and so drawing the containep 

 air into its body. Schmidt-Schwedt believes that the pair of openings 

 are made not by the mouth but by the spines, and that the air is 

 drawn in by internal channels running along them."t 



MacGillivray, in his paper on " Aquatic Chrysomelida3,"X states 

 that the larva of [Hamwnia iiujricurnis, Kirby] can be recognized from 

 that of Donacia by having the sixth and seventh abdominal tergites 

 each armed with a double row of setae, most of which are twice as long 

 as those found on the other tergites, and the supra- spiracular setae 

 wanting. 



The cocoon (fig. 3) is subcylindrical; obtuse-ended, semitrans- 

 parent, smooth and glassy looking, varying in colour from yellowish 

 brown to darker brown. When the beetle is mature, its markings can 

 plainly be seen through the semitransparent walls of the cocoon. The 

 usual place of attachment is to the stems of the food-plant, a few inches 

 above the roots, there ljeing sometimes three or four cocoons on a stem. 

 I have also found them at the roots spun up among the suckers. I am 

 indebted to Commander J. J. Walker for the accurate drawings by 

 Miss M. A. Sharp of the larva, breathing apparatus, and cocoon. 



Oxford: October 6th, 1911. 



*Berl. Entom. Zeitschr., xxxi, pp. 325-334, Taf. v, figs. 1-11 (1887). 



t Dewitz (Berl. Entom. Zeitschr., xxxii, p. 5, 1888) believes that in Hcemonia, and pre- 

 sumably in Donacia also, the spiracles serve for admission of air to the body as Siebold main- 

 tained. Schmidt-Schwedt has, B.E.Z., 1889, reaffirmed his original statement. 



X Hull. X. York State Museum, 'ig, Entom. 18, p. 314(190:'.). 



