SEARCH BEHAVIOR ASSOCIATED WITH EGG CANNIBALISM IN TOXORHYNCHITES-AMBOINENSIS AND TOXORHYNCHITES-RUTILUS-RUTILUS (DIPTERA, CULICIDAE)

Observations based on time-lapse video recordings were used to study b ehavior associated with egg cannibalism in fourth-instar Toxorhynchite s amboinensis (Doleschall) and Tx. r. rutilus (Coquillett). Analysis i ndicated that, once triggered by finding of the first egg, larvae of b oth species engaged in a systematic search of the water surface in an attempt to find additional eggs, which were often seized and eaten. Se ven behavioral elements were identified in the search repertoire, and their relationships studied by analysis of a matrix of preceding and s ucceeding behaviors. The pivotal behavior was ''sweep-adjust,'' which accounted for 87.2% of the time budget in Tx. amboinensis and 73.3% in Tx. r. rutilus. Activity in sweep-adjust consisted predominantly of s ide-to-side sweeps of the head, held just below the surface, punctuate d by small forward adjustments of position. Quantitative aspects of th e sweep arcs, in terms of angular and linear velocity, were determined for the two species. Eggs encountered during search probably were det ected by mechanoreception, only within a very limited, kidney-shaped z one (area almost-equal-to 9.8 mm2) centered at the anterior margin of the head. Eggs were seized with the lateral palatal brushes but withou t head extension as seen in strikes at subsurface prey.