CHAPTER XII 



ORDER EPHEMERIDA* 



The May-Flies 



The members of this order have delicate membranous wings, which 

 are triangular in outline and are usually furnished with a considerable 



number of intercalary veins and with many 

 cross-veins; the hind wings are much small- 

 er than the fore wings and are sometimes 

 wanting. The mouth-parts of the adults are 

 vestigial; those of the naiads are fitted for 

 chewing. The metamorphosis is incomplete. 



The May -flies or ephemerids are of ten 

 very common insects in the vicinity of 

 streams, ponds, and lakes; frequently the 

 surface of such bodies of water is thickly 

 strewn with them. They are attracted by 

 lights ; and it is not an uncommon occur- 

 rence in siimmertime to see hundreds of 

 them flying about a single street-lamp. 



The May -flies are easily distinguished 

 from other net-winged insects by the 

 shape of the wings and the relative sizes 

 of the two pairs (Fig. 350). 



The mouth-parts of the adult are 

 vestigial, as these insects eat nothing in 

 are very small; they are composed of 



350.— A May-fly. 



this state. The antennas 

 two short, stout 

 segments s u c- 

 ceededbya slen- 

 der, many-joint- 

 ed bristle. The 

 thorax is robust, 

 with the meso- 

 thorax predomi- 

 nant; the great 

 development of 

 this segment is 

 correlated with 

 the large size of 

 the fore wings. 

 The abdomen is Fig. 351 



long, soft, and 

 composed of ten 



Caudal end of abdomen of Siphlurus alternatus, 

 male: g, 10, 11, abdominal segments; c, cerci; w/, median 

 caudal filament ; ^, penis;/, forceps-limbs. (After Morgan.) 



*Ephemerida, Ephemera: ephemeron {i<p-^fx€pov) , a May-fly. 



(308) 



