442 



NEUROPTERA 



are enhanced in effect by the ocular structures of the Insects. 

 It has recently been ascertained that a species of Teleganodes 

 is itself luminous. Mr. Lewis/ who observed this Insect in 

 Ceylon, states that in life the whole of the abdomen was lumin- 

 ous, not brightly so, but sufficient to serve as a guide for captur- 

 ing the Insect on a dark night. It has also been recorded that 

 the male of Caenis dimidiata gives a faint blue light at night. 

 Nearly 300 species of Ephemeridae are know^n, but this 



may be only a fragment of what 

 actually exist, very little being 

 known of may-flies of other 

 parts of the world than Europe 

 and North America. One of the 

 more curious forms of the family 

 is Oniscigaster wakefieldi ; the 

 body of the imago is unusually 

 rotund and furnished with lateral 

 processes. In Britain w^e have 

 about forty species of may-fly. 

 The family is treated as a distinct 

 Order by Brauer and Packard, and 

 is called Plectoptera by the latter. 

 That Insects so fragile, so 

 highly organised, wdth a host of 

 powerful enemies, but themselves 

 destitute of means of attack or 

 New defence, should contrive to exist 

 at all is remarkable ; and it 

 appears still more unlikely that such delicate Insects as 

 Ephemeridae should leave implanted in the rocks their traces 

 in such a manner that they can be recognised ; nevertheless, 

 such is the case, indeed, the may-fly palaeontological record is 

 both rich and remarkable. Several forms are preserved in 

 amber. In the Tertiary bed of the old lake at Florissant, Scudder 

 has been able to distinguish the remains of no less than six 

 species ; while in the Jurassic layers of the Secondary epoch, in 

 more than one locality, the remains of several other species 

 have been detected and described. Still more remarkable is the 

 fact that in the Devonian and Carboniferous lavers of the 



Fig. 284. Oniscigaster wakefieldi. 

 Zealand. (After M'Lachlan.) 



^ P. ent. Soc. London, 1882, p. xiii. 



