ABSTRACT
An investigation of the larval dragonfly fauna associated with the plant, Sagittaria platyphylla, was conducted in a small pond. Despite the presence of several larval anisopteran species in the pond, only Pachydiplax longipennis larvae were found on Sagittaria plants. A study of the microspatial distribution of P. longipennis larvae on S. platyphylla indicated that larvae use the various regions of a plant in a highly non-random fashion. Larvae show a strong preference for the leaf axil area. A generalized predator, the bluegill sunfish (Lepomis macrochirus), was allowed to selectively eat either of two larvae placed in various plant regions. This experiment indicated that larvae in a leaf axil area were significantly less susceptible to bluegill predation than larvae positioned in other plant regions. The microspatial distribution of starved larvae revealed that larvae with high hunger levels occupied the leaf axil area significantly less than well fed larvae, suggesting 1) larvae do not use these regions as feeding sites, and 2) high hunger levels may induce a behavioral shift in habitat use, with starved larvae forced into areas of high predation risk by the need to fulfill nutritional requirements.
ABSTRACT
Using Rodenstock's Refraktometer refractometry was done on 314 hyperopic children (3--14 years) first after treating with Atropine and some weeks later after Cyclopentolat-hydrochlorid. 53,1% of them showed higher hyperopia after Atropine than after Cyclopentolat, the maximum in difference was 1,75 dptr. In another group of children with Cyclopentolat-treating the residual accommodation was determined by four different methods (Refactometer, Apparatus of Schober, Phoropter in a distance of 5,0 and 0,4 mtrs). The results show a minimum of accommodation 45 minutes after application of the drops under special conditions. These conditions are reported as well as a method of correction of hypermetropia due to the values of refractometry or residual accommodation.
