1987] 
Uetz & Hart sock — Micrathena gracilis 
105 
Methods 
The study sites were located in Mount Airy Forest and Felter’s 
Tanglewood, two deciduous ravine forest city parks in Cincinnati, 
Ohio. Both woods were characterized by a high, patchy canopy and a 
variable understory of shrubs, saplings and wide open spaces between 
vegetation. The dominant tree species were Acer saccharum, Quercus 
alba , and Fagus grandifolia. The two study sites were very similar in 
their physiognomy and were located within 3 km of one another. Two 
sites were chosen in order to minimize any vegetational disturbances 
that might occur during the course of the study due to the placement 
of artificial sticky web traps in the understory vegetation. 
Because of potential bias in sampling insects found in spiders' 
webs, prey preference in orb weavers is best stud ied by examining the 
fate of insects that encounter the web. Observation of Micrathena in 
the field allows a comparison of the prey captured by the spider with 
potential prey items made available to the spider by its web within the 
forest understory. Because the spider was present, these observations 
allow a test of the null hypothesis of no selectivity: that Micrathena 
actively attacks all types and size classes of insects sticking to its web 
in proportion to the rate at which they are encountered. 
Adult female Micrathena were observed for a total of 77 web hours 
(No. of webs X hours observed) between 1 August and 10 September 
1981. After locating the web(s), the observer sat on a stool 1 to 1.5 m 
from the web(s). This distance allowed close observations of even the 
smallest insects striking the web, but was far enough away not to 
disturb the spider. Observations took place during the normal diur- 
nal activity period for this species, between 0800 hrs and 1 800 hrs, and 
lasted from 1 to 2 hours at a time. Up to three webs could be observed 
at once if they were clumped within 1 to 2 m of one another. 
When an insect struck the web, its length (estimated by holding a 
mm scale close to the web) and taxon were recorded. The insect’s 
“fate” in the web was then followed. (It should be noted that the “fate” 
of insects already present in the web at the beginning of the observa- 
tion period was not recorded. This was done in order to prevent 
over-estimating the number of small insects that actually came in 
contact with webs (i.e. larger insects may have contacted the web and 
escaped — while the smaller ones were trapped and remained in the 
web — and the observer has no way of knowing the former unless he 
or she was present). An insect that struck any part of the orb was 
