SYXOPSIS OF THE BRITISH EPHEMERID^. 3 



^vitll dark rings. The legs are generally pale, but often the 

 joints are darker; the anterior legs not iinfrequently are 

 darker than the others. The wings are generally trans- 

 parent and hyaline, rarely dull ; sometimes yellowish or 

 brownish, or with dark spots; the costa, especially towards the 

 apex, is often darker. The colouring in the sexes is often very 

 different ; the females being always the palest and having the 

 abdomen unicolorous, when in the male it is of different colour. 



The larvae have almost the form of the imago, but yet are 

 generally very unlike it; they are elongate-cylindrical or 

 flattened, sometimes anteriorly much expanded. The strongly 

 developed maxillary organs are adapted for carnivorous 

 habits. The head is much larger than in the imago ; on the 

 sides of the abdomen are six or seven pairs of branchial tufts 

 or plates ; at the apex are three caudal setag, often feathered. 

 The pupa is only distinguishable by the appressed triangular 

 winci^-cases. Pictet's beautiful work frives detailed informa- 

 tion on the larvae, and is the best guide for the student. 



The larvffi always live in the water, are very active, power- 

 ful and predacious ; some genera lurk in holes in the mud at 

 the sides of streams, others swim freely or await their prey 

 under stones. 



The pupae of the Ephemeridce are metamorphosed into 

 the winojed sub-imasfo, which in a short time again casts its 

 skin and appears as the perfect imago. Hence, in this way, 

 the Ephemeridce have one metamorphosis more than other 

 insects, yet some (especially the female of Palingenia longi- 

 caudci) always remain in the sub-imago state, and never 

 cast off the last skin. In the " Stettin Entomolooische 

 Zeitung," 1849, p. 365, I have given a detailed description 

 of the mechanism of this last metamorphosis. The circum- 

 stance, that thus for each species there are four different 

 winged forms (two for each sex), has much increased the 



b2 



