1985] 
Forrest — Balloon-carrying empidid 
291 
females that now held but did not eat the balloons. Males held 
females by the thorax with their enlarged forelegs. Pairs kept in vials 
remained coupled for 2-6 min. 
Some couples left swarms and hovered at the edge of the woods. 
Once swarming ceased, more pairs were found flying near the 
wood’s edge. Due to failing light pairs could not be followed for 
more than a couple of minutes during which time pairs never separ- 
ated or landed. 
Females are significantly smaller than males in both wing length 
and hind femur length. However, males that were captured while 
mating did not differ significantly in femur length but had signifi- 
B 
CD 
> 
O 
O 
~o 
=5 
o 
O 
25 
50 ■ 
c 
CD 
0 75 
CD 
Q_ 
start 
— I - 
stop 
~ 1 — 
L ,i i i i i i— — ■ 
-5 ss 5 10 15 20 
Minutes Relative to Sunset Css] 
Figure 3. A. Average starting and stopping times of swarming for 12 nights (1982 
and 1983). Vertical lines are means, horizontal lines are ranges, and bars represent 
95% confidence intervals of means. Average duration of swarming is time between 
average start and stop. B. Daily duration of swarming for 12 nights in 3 A relative to 
cloud cover at the beginning of swarming. Duration shown for clear days (0% cloud 
cover) is the average for 7 nights. Note the correlation between cloud cover and start 
and stop of swarming (r = —.81, —.90, respectively). 
