Methods for collection in the laboratory of many thousands of eggs from field-collected, blood-fed females are described. Also a way of separating fertile from infertile eggs is outlined. When the eggs are laid they are white but begin to darken within one-half hour. The darkening did not occur when the egg cell or early embryo was killed.Two changes in permeability in the prediapause stage of the eggs of Aedcs hexodontus were observed. The first took place as the chorion changed from white to black. The egg lost and gained water easily when first laid but resisted water loss and uptake as the chorion darkened. However, a complete waterproofing did not result. With the formation of the transparent cuticle a further change in permeability occurred. The egg lost hardly any water even when exposed to extreme desiccation and what little water was lost was regained very slowly. However, the cuticle, with the chorion removed in sodium hypochlorite, was quite permeable. The impermeability of the chorion and cuticle combination must result from the bonding between the two and this bonding must be disrupted by the dechorionation.To study the obligate diapause that occurs in the late embryogeny of the mosquito egg the effect of making water available to the embryo, of light, and of low temperature was studied. Diapause was not broken when water was available to the embryo, nor did alternate periods of light and dark at room temperature or at lower temperatures disrupt the diapause. To test the influence of cold the temperature of 1° and −3 °C. were used to simulate the temperatures in the field. The low temperatures were found to terminate the diapause but the numbers of eggs hatching did not steadily increase with an increase in the time of exposure to cold. No clue has as yet been discovered to explain these results. A hatching infusion of decaying adult mosquito bodies in distilled water was found to give more hatching than did distilled water alone. The mechanism of the hatching stimulus is not known.

At 65" F, the percentage of larvae of the European corn borer entering diapause increased from practically 0 to 95 as the photoperiod was increased from 0 to 9.5-14 hours of light per day, and decreased sharply to a minimum of 3 as photoperiod was increased to 16 or more hours of light per day. Rearing and studies on oxygen consumption revealed that, to be most effective, exposure to factors inducing diapause must begin before the second day of the final instar, and must continue for a period equivalent to the duration of the final instar a t 65" F. Exposure during a n y single instar but the last was not effective in inducing diapause.

No abstract

During the present study we tested the influence of the gas concentrations found in logs on the behavior of Orthosoma brunneum larvae. We also tested gas concentrations far higher than found in nature. Feeding larvae gather in places containing over 0.03% CO2; where a choice of 0.03–100% CO2 is available, they select the place containing 30–50% CO2. They do not congregate selectively in varied concentrations of O2, N2, or CH4. When the larvae cease feeding, although active, they no longer gather in places containing a higher concentration of CO2 than 0.03%. These findings are related to the occurrence of the larvae in the natural environment.

The gaseous microenvironment of Orthosoma brunneum within decaying beech logs is investigated. The cores of rotting logs and mines of insects within the cores contain uniform concentrations of O2 and CO2. The larvae and the pupae of the beetle inhabit wood containing a minimum of 2% O2 and up to about 15% CO2. Wood containing less than 2% O2 is not infested. Wood temperature and moisture determine the concentrations of the gases in the wood: O2 and CO2 are low in the spring, both increase in concentration during the summer; O2 reaches a maximum while CO2 falls to a minimum in the winter.