124 
Psyche 
[Vol. 90 
Materials and Methods 
The study was conducted between July 23 and August 25, 1980, 
on Barro Colorado Island (BCI), Panama. This time period falls 
near the middle of a rainy season which annually extends from late 
April to mid-December (Croat 1978). The island is covered by a 
lowland tropical moist forest (Holdridge et al. 1971). Alpaida tuo- 
nabo was most abundant on the island’s central plateau, and all 
work was conducted there. 
Very little is known about the biology of A. tuonabo. A descrip- 
tion of the female has been published (Chamberlin and Ivie 1936), 
but males have not yet been described (H. Levi, pers. comm.). 
Females are relatively small; the mean wet weight and body length 
of 8 adult females were 0.023 g (SD 0.005) and 5.6 mm (SD 0.94), 
respectively. Females appeared to construct and tend webs during 
the day and consume them at night. In 4 nights of searching, I never 
saw a female or an intact web. On BCI A. tuonabo is abundant only 
in the mid to late wet season (July to December) and is rarely found 
during the rest of the year (Lubin 1978). 
Flying insects were sampled at 10 different sites. At each site I 
implanted a 2.7 m PVC pole (diameter 25 mm) by driving 0.30 m — 
0.45 m of its length into the ground. Wooden rods (length 30 mm; 
diameter 5 mm) were then fastened to the pole at 0.3 m intervals 
(from 0.3 m to 2.1 m above ground). Fastened at one end, each rod 
projected perpendicularly from the vertical pole and hence was 
parallel to the ground’s surface. Insects were collected on tanglefoot 
covered traps suspended from the wooden rods. Each trap was 
a 15 cm by 23 cm rectangle of 3 mm thick transparent plastic coated 
on both sides with tanglefoot. Insects were sampled during the day 
only on August 7-9. Each day the traps were set between 0800 
hrs-0900 hrs, taken down between 1600 hrs-1700 hrs, and stored 
overnight in closed boxes. Aside from Diptera and Hymenoptera, 
all trapped insects were identified to order. Flies were categorized as 
either nematocerous or non-nematocerous, and hymenopterans 
were subdivided into bees and wasps, parasitoids, and winged ants. 
All trapped insects were measured to the nearest 0.1 mm using a 
dissecting microscope equipped with a disc micrometer. 
Each day of the study 1 walked through different areas of the 
forest (between 0900-1630 hrs) and examined every web encoun- 
tered. All caught items were collected and labelled as either eaten or 
