Electroantennograms (EAGs) were recorded from major workers, queens, and males of the Texas leaf cutting, Atta texana (Buckley) (Hymenoptera: Formicidae) in response to serial dilutions of two alarm substances, 2-heptanone and 4-methyl-3-heptanone, and its trail pheromone, 4-methylpyrrole-2-carboxylate. The lower EAG threshold for major workers relative to queens and males for both alarm substances correlated well with previously reported behavioral bioassays which showed workers to be most responsive to these odorants. Although laboratory behavioral bioassays showed minor workers, queens, and males to have a similar behavioral threshold for the trail pheromone, minor workers were more responsive to higher concentrations of the trail pheromone. However, EAGs revealed queens significantly more sensitive and responsive to the trail pheromone than the other castes. These seemingly enigmatic results are discussed with regard to A. texana biology and receptor physiology.
Dicofol was applied to bean leaf discs in various ways. The number of drops per disc, the concentration of dicofol in each drop, and the size of the drops were related to egg laying and mortality of adult female mites placed on the discs. Under the conditions of the experiment, an increase in concentration above normal field strength (0.046% active ingredient) had little effect, even though the deposits were discontinuous and similar to those expected from low-volume spraying. Repellency of dicofol to mites was reaffirmed and toxicity effects were significant when about one-quarter of the leaf surface was covered by deposit.
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