Author: TELFORD ALLAN D.
Publisher: Entomological Society of America
ISSN: 1938-2901
Source: Annals of the Entomological Society of America, Vol.56, Iss.4, 1963-07, pp. : 409-418
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Abstract
Aedes nigromaculis (Ludlow), an inland pasture breeder, survives the principal adversities of its habitat by remaining dormant in the egg stage. Laboratory hatching experiments and field observations supported the hypothesis that its hibernation in Central California constitutes a true facultative diapause of the mature embryo within the egg. Temperature plays a major part in the development and termination of this diapause. Temperature gradients of descending values initiate diapause development in the fall and temperature gradients of ascending values cause the termination of diapause in the spring. Hence, because of the effect of temperature gradients, a single temperature value (particularly in the range of 60° to 70° F.) may tend to initiate diapause in the fall, but conversely, may tend to terminate diapause in the spring. Aedes dorsalis (Meigen), a coastal saltmarsh breeder, exhibits a facultative diapause similar in kind to that of A. nigromaculis. Aedes squamiger (Coquillett), another coastal marsh breeder, undergoes an obligatory diapause in the egg stage during the summer. Circumstantial evidence suggested that its diapause is terminated in the fall by temperatures of 40° F. or lower. Limited hatching responses by A. nigromaculis and A. dorsalis in distilled water, as well as observational data, indicated that a reduction of free oxygen in flooding media may not be required for the hatching of all Aedes eggs under all circumstances. In its capacity as a hatching stimulus, the reduction of free oxygen is considered to be independent of the diapause phenomenon in these species. However, in these cases the stimuli which inhibit or terminate facultative diapause commonly act in concert with a reduction of free oxygen when eclosion occurs in nature.