NEUROPTERA. 



Synopsis of the British Ephemerid^. 

 By Dr. Hagex. 



EPHEMERID.E. 



Body long and narrow ; head rather small, but little broader 

 than long ; antennas slender, short, pointed ; with two short 

 thicker basal joints and a fine bristle of greater length. Eyes 

 generally large, of very different forms in the two sexes, but 

 always further apart and smaller in the females, in the males 

 sometimes very large, conical and placed near together. The 

 males in two genera have double eyes, in which an upper 

 segment branches off either as in many Ascalaphi (Pota- 

 manthvs) through a lateral furrow, or in the form of a 

 turban-like excrescence, which is generally brightly coloured 

 (Cloeon). On the flat crown are the small ocelli remote 

 from each other. The maxillary organs are undeveloped 

 and unfit for eating. The prothorax is annular, sometimes 

 very short. The mesothorax is very large, stout and barrel- 

 shaped. The metathorax is small and sometimes ill-developed. 

 Abdomen ten-jointed, long, cylindrical or flattened, generally 

 attenuated towards the apex, beneath the dorsal plate of the 

 last segment are inserted three long, thin, many-jointed, 

 caudal filaments ; the middle one is sometimes longer or 

 shorter than the others, and in some genera or even as a 

 sexual character is either entirely or almost entirely wanting. 

 The caudal filaments in the male are always considerably 

 longer than those of the female, often manv times long^er 

 1863. B 



