1980] 
Eberhard — Bo las Spider 
167 
Gertsch 1947 suggests, they can live for extended periods). It is 
interesting to note that Celaenia, which hunt without a web, also have 
spines on their front pairs of legs (e.g. Fig. 24 in Forster 1967). In this 
case however the spines are on the ventral surfaces of the femur and 
tibia, and would seem designed to give the spider a more secure grip 
on prey that has already been seized (see however Lowry’s description 
in McKeown 1952 of spiders accepting prey held in forceps) rather 
than to increase the surface of the leg and thus presumably its ability 
to intercept prey as in small M. dizzydeani. 
The variety of prey captured by M. dizzydeani (Table 1) is not 
surprising, given the fact that different moth species have been found 
to use identical sex attractant chemicals (e.g. Silberglied 1976). It is 
however unexpected to see the differences in prey captured by 
different individuals of the same species and size at the same time and 
place. The spiders seem to be somewhat flexible with regard to prey, 
and this trait could obviously be advantageous if, as seems likely, a 
single prey species is not consistently plentiful. How the differences 
between individual spiders are produced is unknown. Although the 
data are meager, it appears probable that M. dizzydeani change 
pheromones as they mature, attracting larger species as they grow. 
This conclusion must remain tentative however pending more data 
on prey, proof that the other prey species actually produce and 
respond to different pheromones, and that the spiders attract them 
chemically. Perhaps the thick-walled egg sacs of Mastophora and its 
relatives serve to protect the young for extended periods so that they 
can emerge when particular prey species are abundant. 
The name “bolas spider” is firmly fixed in the literature, and I do 
not propose that it be changed, but it is worth noting that it is a 
misnomer for Mastophora. A bolas consists of a thong or thongs to 
which heavy balls are attached, and is thrown so that the thong wraps 
around the target, impeding its escape. The Mastophora trap is more 
sophisticated: it depends on the extraordinary stickiness of the ball 
rather than the entangling action of the line; it is swung rather than 
thrown at the prey; and the ball itself converts reversibly into a sticky 
line which increases the spider’s striking distance. A less picturesque 
but more accurate name would be “sticky yo-yo spider . 
Acknowledgements 
1 thank R. Forster and C. S. Lauder for information on Celaenia, 
