418 THE CANADIAN ENTOMOLOGIST 



Explanation of Plates XIX and XX. 

 Fig. 1 — 8. — Apical abdominal segments of Sympetrum nymphs 

 dorsal view. 1, S. semicinctum ; 2, S. vicinum; 3, S. 

 costiferum ; 4, 5. pallipes; 5, 5. ohtrusum; 6, S. riibicundu- 

 lum decisum; 7, S. scoticum; (Red Deer, Alta.) ; 8, 5. 

 scoticiim. (Harz Mts., Germany.) 

 Fig. 9 — 14. — Left lateral view of abdomen of Sympetrum nymphs. 

 9, S. vicinum; 10, S. costiferum; 11, S. pallipes ', 12, 

 S. obtrusum; 13, S. scoiicum; 14, S. ruhicundulum 

 decisum. 

 Figs. 15 — 19.^ — Dorsal view of head of Sympetrum nymphs. 15, S. 

 semicinctum; 16, S. vicinum; 17, S. pallipes; 18, S. 

 scoticum; 19, S. ruhicundulum decisum. 



OBSERVATIONS ON CHIRONOMUS DECORUS 



JOHANNSEN.* 



BY CHI PING, ITHACA, N.Y. 



Chironomus decorus Johannsen is a common species found 

 about Ithaca. The larva, pupa, and imago have been described! 

 but its egg stage was missing, and its habits and development 

 were hitherto unknown. The present work records my observa- 

 tions made in the summer of 1915. 



Flying and mating.- — The adults begin to swarm at sunset 

 and continue into the twilight. At first one or two come out from 

 the grasses, rushes and sedges growing along the shores of pools 

 or ponds where they spent the day. They fly very slowly at 

 first. Later pn, as more and more come out and join them, they 

 become more active. As the nightfall commences they can only 

 be' seen outlined against the sky. A swarm is often found over- 

 head, from 10 to 15 feet above the ground. The swarm continues 

 to increase in size, until a column may be formed about 5 feet in 

 height and 1 fooit in diameter, with its base about 5 feet above the 

 ground. 



While engaged in dancing, all the midges have their heads 

 pointing in the same direction, with their bodies moving back 

 and forth and up and down, sometimes with great rapidity. The 



*Contribution. from the Limnological Laboratory of Cornell University, 

 Ithaca, N. Y. 



tjohannsen, O. A., Bull. 86, N. Y. State Mus., p. 239. 

 December, 1917 " 



