1908] The Dragonflies of the Ottawa District. 63 



The only insect that might be mistaken for L. pttkhella is 

 the female of Plaihemis lydia, which is smaller (hind wing of 

 lydia female, 35 mm., of pidchella female, 41 mm.), and in which 

 the hind femur is about as long as the tibia, while in pulchella 

 it is a little longer. 



53. LiBELLULA QUADRIMACULATA, LinUC. 



Ottawa. May 28th, 1900, 1 male (Gibson); July 18th, 1907, 

 1 male (Letourneau). 



Another familiar dragonfly of unmistakable appearance. 

 Yellowish brown or olivaceous; wings yellovv^ at base' and general- 

 ly along the front margin; a small black nodal spot and a larger 

 triangular black spot at the base of the hind wings. 



L. qnadrimacidata is a northern species and is circumpolar 

 in distribution, being a common species in Europe and Asia as 

 well as Xortli America. 



Genus Plathe.mis, Hagen. 



54. Plathemis lydia (Drury), Hagen. 



Ottawa, Julv 21st. 1907, 1 fem^ale (Young); Mer Bleue, 

 June 18th, 1907,'! male (Fletcher). 



This is one of the commonest of the larger Libellulid?e in 

 central and southern Ontario, but is scarcer northw^ard. 



It exhibits a remarkable sexual dimorphiom, the wings of 

 the two sexes being A'ery different in their markings. In the 

 female these are nearly identical with those of Lihellula pulchella, 

 but in the male the nodal and apical spots are substituted by a 

 single broad band crossing the wing from about the nodus to the 

 pterostigma, the apices being clear. In old males there is a 

 triangtilar white patch behind the basal stripe of the hind wings 

 and the abdomen is oruinose white. 



In habits and flight P. lydia is quite like the Libelhdce. 



