THE ANNALS 



A.ND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 105. SEPTEMBER 1866. 



XXIV. — Notes on some Species of the Orthopterous Genus Cloeon, 

 Leach {as limited by M. Pictet). By A. E. Eaton, of Trin. 

 Coll. Camb. 



Although but little attention is paid by the generality of ento- 

 mologists to the Ephemeridse, the following notes may prove not 

 altogether uninteresting. From reading Dr. Hagen's introduc- 

 tory remarks to his synopsis of the British species of this family 

 (Ent. Ann. 1863) one might be led to imagine that in their early 

 stages of development they are strictly carnivorous. The exist- 

 ence of such a propensity is clearly seen by merely placing a 

 number of pupae in a small vessel, when the stronger will speedily 

 devour such as they are able to master. But that their diet is 

 partly vegetable also is apparent on an examination of the con- 

 tents of their alimentary canal ; for, in many instances, along 

 with a large proportion of mud, half-digested Diatoms and 

 pieces of Confervse can be detected. These the animals obtain 

 by nibbling over the surface of water-plants and stones — an oc- 

 cupation to which they are much given. For this work their 

 jaws are admirably suited. In the front are four or five strong 

 sharp teeth, arranged in two rows, whilst behind these is a very 

 singular structure — a flattened transversely striated protuber- 

 ance, somewhat resembling an elephant's tooth in miniature*. 

 Their subulate antennae and their unconcentrated abdomen are 

 not the only points in which they resemble Libellulidse, as, be- 

 sides the branchial plates of the pupa, the rectum is subservient 

 to purposes of respiration. They seem to be furnished with a 

 muscular cloaca, which is shut off from the extremity of the ali- 

 mentary canal by a voluntary sphincter muscle. Its external 

 aperture is the anus, through which water is admitted when the 

 insect wishes to inspire. The cloaca being filled, this is then 

 closed, the rectum opens, the cloaca contracts and forces the 

 * Jaw of the pupa of Ephemera vulyata, L. 

 Ann. i^ Mag. N. Hist. Ser.3. Fo/.xviii. 11 



