1975] 
Robey — Pachydiplax longipennis 
93 
behavior may be primarily thermoregulatory in function rather than 
purely for territorial display as concluded by Johnson (1962). 
Mating and Oviposition 
Pachydiplax females were infrequently seen at the three ponds. 
During July and August only 25 matings were closely observed. 
Females appeared between 1300 and 15°° hours (E.S.T.) on warm 
sunny days and courtship commenced immediately. A territorial 
male, upon seeing a female within his territory, would fly directly 
to a position above her. Hovering a few centimeters above her he 
would raise his abdomen in a manner similar to that seen in the 
threat display. (But in a position that makes it difficult for the 
female to see this display.) He then flaps his wings rapidly in an 
unusually wide arc. A receptive female will permit the male to 
align his body directly above hers. The male then descends and the 
female rises up slightly while lowering her abdomen and presenting 
her head (Fig ic). In rapid sequence he clasps her with his ab- 
dominal appendages and they go into copula. Copulation occurs in 
flight and is brief, lasting 10-40 seconds. Its duration appears to 
depend, in part, on the number of previous inseminations received 
by the female, but only by collecting data could this speculation be 
verified. The pair then separate and the male returns directly to his 
display perch. On three occasions the male was seen to transfer 
sperm to his genitalia during this short postmating flight. Typically, 
the female also rests for 5-10 seconds on a nearby perch before 
searching for oviposition sites. 
Oviposition was observed as illustrated by Needham and Westfall 
( 1 95 5 ) . I found that the male defended the female from interfer- 
ence by other males only as long as she remained within his terri- 
tory. The flight of these defending males was more directed and 
intense than that seen in male-male interactions. Nonetheless, in a 
few cases, when many males were present and/or when the female 
strayed out of her mate’s territory, his fervent defense was inade- 
quate and oviposition prevented. A behavior, marked in Libellula 
incesta Hagen but less common in P. longipennis, occurred when 
unmated males attempted to grasp the female while her head was 
exposed during oviposition. The female was usually knocked, tum- 
bling, into the water. L. incesta females, being stronger fliers, would 
attempt to evade such attacks; P. longipennis females usually re- 
treated to the trees until male excitement diminished. In addition 
to interference from other males, frogs presented a major threat to 
females ovipositing near the edge of the ponds. 
