80 
Psyche 
[March 
Acacia (?) trees and numerous unidentified shrubs, forbs and 
grasses. This roadside area was bordered on one side by a large 
cornfield and on the other by an irrigation ditch. A second roadside 
area was perpendicular to the first, bordering the same cornfield. 
This site has a larger irrigation ditch, the sides covered by dense, low 
growing willows (Salix sp.). A third site, a maguey plantation, was 
located approximately 1.2 km east of the other sites. The area was 
planted in large (>1.5 m) Agave (approximately 5-7 yrs old), 
interspersed with grasses and occasional trees. The plantation has 
the appearance of an Agave “orchard”, due to the semi-regular 
dispersion of the large plants. These three areas represent the char¬ 
acteristic habitats where Metepeira were found in the Tepotzotlan 
area. 
To assess habitat preferences of Metepeira, a series of 6 200 m 2 
quadrats was delineated in the roadside area containing a variety of 
vegetation types. Within each quadrat, the percent cover and per¬ 
cent volume of each vegetation type was estimated. Frequency of 
occurrence of Metepeira spinipes, (both colonies and solitary indi¬ 
viduals) was recorded within each vegetation type. 
In both the maguey plantation and the roadside ditch covered by 
willows, counts were made of spider group size. In addition, meas¬ 
urements of colonial web dimensions and habitat dimensions were 
made for selected groups. 
Results and Discussion 
The web of individual Metepeira spinipes is characteristic of the 
genus, and is a three-dimensional space web/ orb web composite 
with a retreat in the space web (also called a barrier web; Levi 1977) 
(Fig. 1). Signal threads connect the hub of the spiral and the retreat, 
where the spider rests (Burgess & Witt 1976). Only the threads of the 
orb’s spiral are sticky, and the orb is the primary prey catching 
device. Prey are often entangled in the space web and occasionally 
are caught there. Individuals of M. spinipes in Central Mexico usu¬ 
ally occur in aggregations, although solitary individuals of this spe¬ 
cies are also found. Most of the groups we examined consisted of 
5-30 individuals, but much larger groups (50-80) were seen. In the 
groups we observed, individuals had their own retreats and orbs but 
space webs were joined. Although orbs are usually renewed on a 
daily basis (spiders rebuild radii and sticky spirals during the night) 
