droelectric projects, the Rondonia project, and various other development projects that are starting to break up that vast expanse of forest. From the air, one can detect even finer and finer mosaics. It is very easy to pick out the trees in blossom, the trees with tough dark-green leaves, trees that lost their leaves during the dry season and are now getting a new flush of very light pale leaves (the ones the insects like to eat the most), and vines that reach up into the canopy to spread their leaves over the tree leaves or intermingle them with the leaves of the canopy trees. All 150 or more species of canopy trees or vines per hectare contribute to the mosaic. There is an intermingling of leaves between two species of trees, between the vines and the trees, and between one tree overshadowing the other, resulting in the creation of microenvironments for the little creatures that are so important in providing the richness of the world’s biotic diversity.
Depending on forest type, the tops of the trees range from 15 meters to as high as 55 meters. Tambopata was chosen for my preliminary studies because logistically it is very difficult to get equipment and people into a virgin rain forest, keep them there for long periods, and get the material back to the museum to study it under the microscope. The average length of the beetles in the canopy is about 2 to 3 millimeters, so one needs pretty good facilities to make detailed studies. Tambopata served the logistic purposes as well as another purpose—approximately 11 different types of forests are found within walking distance. That seemed like too much to handle during 1 year, so only five were selected for intense collecting. In each of these five forests, we selected three 12-meter-square plots (Erwin, 1983b).
All 15 plots were sampled in the early rainy, late rainy, early dry, and late dry seasons. The data collected included tree canopy sizes, species of trees, and exact location of the collecting trays. All this information has been computerized and allows museum specimens to be traced back to the actual square meter of rain forest where they were collected. This gives us the opportunity to return in subsequent years and resample in order to see what the canopy, or what the forest in general, is doing over long periods. Long-term cycles have been largely overlooked, except by a few researchers for only a few species. My research team is now beginning to computerize the canopy in three dimensions so that we can describe exactly where these insect species reside in the canopy.
Beyond this data set, we also have the branching patterns, the leaf structure, and other details of microhabitats. It has taken a long time to develop our data collections, because we have paid attention to the finest details. I am trying to look at the canopy habitat through the eyes of these 2- to 3-millimeter-long beetles.
To date, we have analyzed about 3,000 species of beetles from only five plots. When we complete our analysis, we will have a large data set. A comparison of the tree composition of the different kinds of forest has shown that the forest in Manaus and two of our upland terra firma forests contain entirely different tree families. There are more big trees in the Peruvian sites than in the Manaus sites. Perhaps that accounts in part for the larger size of the insects in the canopy in Peru than in Manaus.
Only 2.6% of the species are shared between Manaus and Tambopata (Figure 13–2). This seems reasonable, because the two sites are 1,500 kilometers apart.