| Summary: | The life history and wing pattern variation of the intertidal
shore bug, Saldula palustris (Douglas), were studied in field and
experimental populations from June 1970 until February 1972.
The study site was an estuarine salt marsh on Yaquina Bay
near Toledo, Oregon. The insects live below mean high water level
and are regularly submerged by the tide for up to ten hours. Behavior
of S. palustris upon submergence is well adapted to the intertidal
habitat.
Overwintering occurs in the adult stage and adults migrate
from the intertidal area in late fall, The reproductive period begins
upon their return in February with mating, egg development, and
oviposition and ends in September with cessation of these activities.
The first adults of the spring generation appear in mid-May. There
are three generations a year and reproductive diapause in fall and
winter is facultative.
Mean adult wing darkness (based on percent dark area in wing
membrane) in field collections varied from palest in mid-summer
(45-50% dark) to darkest in late fall (65-70% dark). Males and
females were in general not significantly different in wing darkness.
Wings of females are longer (and wing membrane area larger)
than those of males. Maximum wing lengths were found in adults
collected during the spring and late summer. Wing darkness was
not associated with wing size in each sample but correlations over
time, related to the emergence of the different generations, were
observed. Aging had no effect on the extent of pigmentation in adult
wings.
Temperature effects on the insects were investigated in some
detail since previous reports showed that temperature was a major
factor influencing the life history and morphological variation of
insects. Developmental threshold temperatures, determined in the
laboratory for S.palustris (10° C for embryonic development and
hatching, 15° C for development to adult), were correlated with mean
field temperatures and the first and last appearance of the various
developmental stages in the field in spring and fall.
Temperature had the greatest effect on resulting adult wing
darkness during the third and fourth nymphal stages, cooler
temperatures producing darker adults. Similarly, cool rearing
temperatures produced significantly darker fifth instar cuticles if
the nymphs were subjected to the lower temperature prior to the
fifth instar. As with adults, nymphs do not darken after hardening
following the moult.
Adults reared from the fourth instar stage on a black substrate
had significantly darker wings than adults reared from similar
age on a white substrate. === Graduation date: 1972
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