268 



PHILIP P. CALVERT. 



August, and from 20 to 5 during September. The species which 

 continues to fly latest into the Autumn is Diplax vicina, having been 

 observed up to October 26, and probably to be found still later, as 

 Mr. G. D. W. Williamson has taken it at Dobb's Ferry, New York, 

 on November 8. The maximum number of species on the wing at 

 any one time is thus 32 from June 24 to July 1. 



TABLE SHOWING THE SEASONAL DISTRIBUTION OF THE SUBFAMILIES 

 OF THE ODONATA OF PHILADELPHIA. 



Subfamily. 



Calopteryginse 



Agrioninffi 



Gomphinse 



Aeschninse 



May 1 

 Gomphus exilis, 



May 24. 

 Anax Junius, 

 May L 



CorduliuEe D. transversa. 



May 13. 

 Libellulinse 



Earliest appearing 

 species. 



Calopteryx maculata 

 May 24. 



Latest appearing 

 species. 



Hetserina americana 

 Sept. 23, 



I. verticalis, N. posita I. verticalis, 



Oct. 16. 

 Gomphus plagiatus, 



July 17. 

 Aeschna constricta, 



Oct. 18. 

 Epicordulia princeps 



July]. 



P. trimaculata, L. 

 semifasciata, May 

 17. 



Maximum number 



of species at 



one time. 



Diplax vicina, 

 Oct 26. 



Two, Aug. 11-17. 



Thirteen, June 28- 



July4. 

 Four, June 22-26. 



Four, A ug. 28-29. 



Three, June 18. 



Thirteen, July 5-22. 



GEOGRAPHICAL DISTRIBUTION. 



Of the 33 genera represented in the foregoing list, 8 (^Dromogom- 

 phus, Gomphceschna, Didymops, Epicordulia, Tetragoneuria, Plathe- 

 viis, Nannothemis, Pachydlplax) are exclusively Nearctic, 8 {Hetairma, 

 Aviphiagrion, Anomalagrion, Ejnceschna, Micrathyria, Cellthemis, 

 Periihemis, Mesothemis) are confined to the New World, 3 {Calop- 

 teryx, Fomcolombia, Leucorhinia) are restricted to the Palsearctic 

 and Nearctic provinces, while the remaining 14 are more widely 

 distributed. 



The great majority (49) of the sixty-six species of the preceding 

 list are confined to the Alleghenian subdivision of the Nearctic zoo- 

 geographical province, i. e. to that portion of the United States east 

 of the Rocky Mountains. Of the remainder — 



Pantala flavescPMS is a well-known cosmopolitan species. 



Aeschna juncea and Libellula quadrimaculata are diffused through- 

 out the northern hemisphere. 



Ischnura Ramburii, Anomalagrion hastatwn, Anax Junius, Pantala 

 hymencea, Celithenns ep)onina, Perithemis domitia and Mesothemis sim- 

 pllclcolVis are also West Indian. 



Lestes forclpata, A)iax Junius, Libellula quadrimaculata, Diplax 

 Hemicincta and D. corrupta also occur in the region between the 



