CHAPTER XII 



ORDER EPHEMERIDA* 



The May-Flies 



The rAembers of this order have delicate membranous wings, which 

 arc triangular in outline and are usually furnished with a considerable 

 number of intercalary veins and withmany 

 cross-veins; the hind wings are much small- 

 er than the fore wings and arc sometimes 

 wanting. The matt th-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 summertime 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 



Fig- 350-— A May-fly. 



The antennas 

 stout 



this state, 

 two short 

 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 

 long, soft, and 



composed of ten 



351. — Caudal end of abdomen of Siphlurus alternatus, 

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

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



*Ephemerida, Ephemera: ephemeron {icp-nM^pov) , 

 (308) 



May-fly. 



