1979] 
Eberhard — Argyrodes attenuatus 
411 
Fig. 3. Same as Fig. 2. Note that the sticky line is held on the lateral surface of the 
spiders right leg IV. The line to the left of the A. attenuatus is coated with white 
powder, while that to the right is uncoated and thus invisible. 
Spilasma artifex spiderlings consistently escaped because they did 
not stay on the A. attenuatus lines, but descended on lines of their 
own, and as the A. attenuatus approached them or tried to reel them 
in, they let out silk faster until the A. attenuatus finally turned away. 
As noted by Eberhard (1980) and Lahmann and Zuniga (in 
prep.), it is common to find small insects, mostly nematocerous flies, 
hanging at night from spider threads in some forested areas. These 
“trapeze” flies seem to prefer more or less horizontal lines, but do 
not discriminate between threads from different spider species, and 
will even hang on cotton thread (Lahmann and Zuniga in prep.). 
Young A. attenuatus were frequently found with small flies as prey, 
and the supposition that these prey had been captured while 
hanging on the spiders’ webs was reinforced when I observed an 
attack on such a fly. When I first noticed the fly, it was hanging on 
one of the threads of a spider’s web, and the spider was about 5 cm 
away, facing toward it. As I watched, the spider moved very slowly 
and smoothly toward the fly, stopping frequently to hang motionless; 
it took nearly five minutes to cover the 5 cm. There were occasional 
gentle vibrations of the line, but I could not tell whether they were 
caused by the spider or a sporadic gentle breeze. As the spider 
neared the fly, it began waving its front legs slowly; it touched the fly 
