OBSERVATIONS ON BREEDING BEHAVIOR OF 
PACHYDIPLAX LONGIPENNIS 
( ODONATA :LIBELLULIDAE ) * 
By Carol Walser Robey 
Museum of Comparative Zoology 
Cambridge, Mass. 02138 
Introduction 
Pachydiplax longipennis Burmeister is a medium sized dragonfly 
found throughout the United States. Clifford Johnson (1962) has 
described the general pattern of breeding behavior of this species in 
North Carolina, Virginia and Texas. In this paper I report my 
observations of three populations of this species in Massachusetts. 
While territorial and mating behavior is similar to that described 
by Johnson, I am able to extend his findings in some areas. In addi- 
tion, I describe the coloration of this species in ultraviolet light and 
speculate as to the behavioral significance of the high reflectancy of 
areas of blue pruinescence. 
Methods 
Observations were made at three ponds near Boston, Massachu- 
setts, during the period June- August, 1974. Pachydiplax longipennis 
was relatively abundant at each pond. Observations were made 
throughout the daily activity period and under a variety of weather 
conditions. 
Initial observations were made at Pickman Pond at the Concord 
Field Station of Harvard University in Bedford from June 13- 
July 18. This is a shallow man-made pond of about 1.5 hectares. 
The banks are thickly vegetated with bushes and sedges; the sur- 
rounding vegetation has been mapped by Maguire et al. ( 1973 ). 
Water depth within 2 m of the shore was typically 20-50 cm. Fallen 
branches and emergent vegetation, such as water lilies, lined the 
periphery. In early July, studies were conducted at a second shallow, 
artificial pond in Lexington (Five Fields: ca. 0.5 hectares), where 
the lack of dense fringing vegetation facilitated detailed observations. 
The pond was bordered on two sides by grassy banks and overhung 
by trees (mostly Acer rubrum) . Emergent vegetation included 
* Manuscript received by the editor May 19, 1975. 
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