738 JOURNAL, BOMB A Y NA TVRAL HISTOR Y SOCIETY, Vol. XIX. 



modified so as to take the place of jaws for capturing prey as in Naucoris, Nepa. 

 and the giant Indian water bug {Belostoma incUca). In Nepa the limbs are 

 very peculiar and are bent inwards and can be closely folded, the fore part 

 having a groove which receives the tarsus. 



The Ephemeridce or May flies have attracted the attention of Natural- 

 ists from early times, and most of our knowledge relating to these 

 beautiful insects are due to the indefatigable labours of Swammerdam, 

 Malpighi, Reaumur and De Geer. When we read that the tools employed 

 by Swammerdam for the dissection of a May fly larva were so fine as to 

 require whetting under a mici'oscope we can truly appreciate the fine 

 work done by him. Though this naturalist wrote in 1675 little further has 

 been added to his knowledge of the Ephemeridce. May flies are extremely 

 delicate insects having the anterior wings largely developed and the posterior 

 small or wanting. They have a rudimentary mouth, and the body ends in two 

 to three long anal setae. May flies are remarkable for undergoing four 

 distinct changes before maturity instead of three. The fly when it first 

 emerges from the pupa resembles the adult fly but is known then to Entomo- 

 logists as a pseudo-imago, that is to say another skin is cast before the insect 

 finally flies away. Another peculiarity of the Ephemeridoi is the short duration 

 of life of the perfect insect, and the popular idea is that they invariably die 

 after the sunset preceding their time of development from pupa to imago. 

 Many of them, it is true, live tor a few hours only, though'aj period of two days 

 is on record, I myself have proved that their vitality is not so feeble as is 

 generally supposed. One specimen was on my setting board for three days and 

 then still retained signs of life, for when touched it responded by gently 

 waving the long setae to and fro although it had previously lain in the killing 

 bottle for quite five minutes. The long hair-like setae when examined under 

 a microscope bear a close analogy in structure with the antennae of many 

 insects, and doubtless serve the function of such, the true antennae being very 

 small. In support of this I have frequently held live May flies by their 

 wings and they invariably moved the setae in exactly the same manner that 

 many insects move their antennae. A similar structure is found in the Mole 

 crickets (Gry^Zoiai^Jo) which possess tail appendages covered with stiff hairs. 

 These act as delicate organs of perception by the insect when moving back- 

 wards in its subterranean progress. I have microscopically detected further 

 abdominal appendages on one species of May fly resembling those of dragon 

 flies. These may be claspers and used by the male to hold the female. Very 

 little is known of the Indian Ephemerkla',. " Less than thirty species are actually 

 recorded but some are quite abundant in rivers " (Lefroy in lit.). Their 

 flight is very pretty to watch. They ascend in a soaring manner with the 

 wings hardly moving, then descending again very rapidly. The eggs of May flies 

 are laid on the surface of the water, the whole quantity being deposited 

 at the same time. The eggs being heavier than the water sink immediately. 

 The larvae when hatched burrow into the mud. Their bodies are composed of 



