No abstract

The abundance of bottom fauna and of fauna in drift was studied in streams treated with DDT at various times in the past. Recovery of the bottom fauna was found to be rapid, but that of drift was delayed. The relationship of quantity of drift to the increasing bottom standing crop during recovery from spray effects was found to be curvilinear. This suggested that drift is a density—related process. Possible mechanisms to explain drift are discussed, and the conclusions of earlier reports on recovery of streams following insecticidal treatment are questioned.

Since the monumental work of Rose (1938) on the essential amino acids for growth in the rat, similar studies have been made on other vertebrates. It has been shown that most of these animals have the same pattern of amino acid requirements for growth of the immature form and for maintenance of nitrogen equilibrium in the adult. The amino acids usually required are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane, and valine. These studies have been adequately reviewed in recent texts (Bourne and Kidder 1953, Albanese 1950).

Emodin, a mixture of anthraquinones, occurs in the Rhamnaceae and functions as a deterrent to foliage-feeding insects. There was little attack on foliage of Rhamnus alnifolia in wild stands compared with associated species of woody plants. Anthraquinones extracted from foliage of R. alnifolia were similar to purchased emodin in thin-layer chromatographic and infra-red spectroscopic analyses. Quantities of emodin in foliage samples were high in May, declining to low levels in August. Leaf powders, leaf extracts, and purchased emodin all showed feeding deterrent activity when mixed with artificial diets and assayed with gypsy moth larvae. Purchased emodin showed similar activity when sprayed on foliage of small cherry trees and assayed with eastern tent caterpillar larvae.

Residue analysis of forest soils sprayed once at 1 lb/acre showed little breakdown of DDT through 9 years after application. In the absence of appreciable downward trend, residue persistence could not be estimated beyond stating that it appears to persist much longer than the 10 years suggested by others. Persistent residues are largely restricted to the upper soil litter. Residues pass from soils to earthworms to robins throughout the 9-year period studied. It is suggested that this relationship may persist for as long as 30 years after a single application to the forest. Biological magnification of residues in robins is demonstrated. Significance of these residue levels is discussed.