1979] Uetz & Burgess — Behavior in M. spinipes 87 
maintenance oi individual space (web defense etc.) would be 
retained. 
There are many other selective advantages to group living that 
might also apply to the evolution of coloniality in M. spinipes. By 
locating space webs together, spiders gain additional “knock-down” 
structures which may serve to increase prey taken. The colonial 
space web creates a stronger foundation on which to build individ¬ 
ual orbs, and may allow energy savings in web maintenance costs. 
The colonial web also transmits vibrations, and may be an impor¬ 
tant means of communication of predator attack or prey availabil¬ 
ity. Prey stealing and web take-over are often seen in M. spinipes 
and other species, and suggest that spiders may benefit from living 
in an aggregation without building a web. The mate selection pro¬ 
cess is facilitated by group living, and males may increase their 
fitness by attending’ a female (we have observed this) before she 
molts to adulthood. Colonies of spiders like M. spinipes can 
monopolize larger, or better quality web sites, while solitary species 
Figure 2. Amount of colony volume per individual M. spinipes over a range of 
colony sizes. (Colony volume in cm 3 is expressed as a cube root for linear comparison 
with number of individuals.) 
