R. Zweifel Journal 9 mi. &N Mazatlan, 100', Sinaloa, Mexico July 16 From a distance, the Thorn Forest appears so dense as to be impenetrable. However, closer examination shows that the lower layer is sufficiently open that it is possible to make a somewhat contorted path through even the thicker appearing parts. The main layer of vegetation stands at 10-12' in height. Above this occasional trees project to 20' or more. There is no definite layer developed below the main layer, only some spotty herbaceous vegetation and agaves in the more open places. Small bromeliads are common on the trees. Numerous vines hang from the trees. Annoying insects form the most abundant animal life. The mosquitoes dance you day and night. Even on the hottest afternoon, to step into the shade is to invite a bloodthirsty swarm. Flying termites were seen in great swarms during the heaviest rainstorms, both day and night. A termite nest 20' up on the left of a tree was seen. It was about 3' x 2' x 2' in dimensions, and reached by the termites via outside of the inch wide tunnels constructed up the trunk. The region swarmed with geometrid larvae which seem to spend most of their time hanging from threads. From this position they land on your neck whereupon they get swatted with the vigor due a mosquito, and respond by squashing green all over you.