Water Bugs

Three basic adaptive responses—regulatory, acclimatory, and developmental—may occur in organisms as they react to changing environmental conditions. In all three, adjustment of biological features (morphological adjustment) or of their use (functional adjustment) may occur. Regulatory responses involve rapid changes in the organism’s use of its physiological apparatus—increasing or decreasing the rates of more time than regulatory response changes. Regulatory and acclimatory responses are both reversible.

Developmental responses, however, are usually permanent and irreversible; they become fixed in the course of the individual’s development in response to environmental conditions at the time the response occurs. One such response occurs in many kinds of water bugs. Most water-bug species inhabiting small lakes and ponds have two generations per year. bugs to search for new habitats, an eventuality that macropterous individuals are well adapted to meet.

The dimorphism of micropterous and macropterous individuals in the summer generation expresses developmental flexibility; it is not genetically determined. The individual’s wing form is environmentally determined by the temperature to which developing eggs are exposed prior to their being laid. Eggs maintained in a warm environment always produce bugs with normal wings, generation, brought into the laboratory during the cold months and kept warm, produce only macropterous offspring.