10 
Psyche 
[March 
Figure 6. Miagrammopes sp. 3 on its web, as seen from below and slightly to the 
side. The brighter threads are sticky (the web was not powdered). Note that the spider 
has broken the end of the capture thread and holds it with the front legs bent to the 
side in a manner similar to that shown for M. simus (Fig. 1 b). 
Stage II: Entanglement of the prey — sagging the line 
The spider sagged the capture thread by dropping the loose silk 
it had pulled in with its hind legs, and perhaps also letting out 
additional dragline. At almost the same time it manipulated the 
capture thread with a series of complex movements of leg I (Fig. 7a) 
which resulted in the prey being jerked rapidly back up and down 
again (Fig. 7b). Whereas the jerks in stage I displaced a fruitfly 
only 5-6 mm, sagging the capture thread caused the prey to drop 
26-33 mm in less than 1/30 second. As the prey dropped, it was 
often displaced sideways as much as 6 mm (due to air currents?). 
Rapid and repeated sagging of the capture thread resulted in the 
formation of one or more loops of silk that enveloped the prey. 
Such loops were seen in the capture threads of both M. simus and 
M. sp. 1. 
The mechanism responsible for the formation of these loops is 
not clear. One possible explanation is that, due to the relatively 
higher air resistance and lower weight of the silk, the prey drops 
more rapidly than the silk during a sag, and therefore falls into 
the silk below it (Fig. 8a). An alternative explanation (Fig. 8b) is 
