Effect of pre-wintering and wintering temperature regimes on weight loss, survival, and emergence time in the mason bee Osmia cornuta (Hymenoptera: Megachilidae)
Apidologie
Effect of pre-wintering and wintering temperature regimes on weight loss, survival, and emergence time in the mason bee Osmia cornuta (Hymenoptera: Megachilidae)
Jordi BOSCH 1
William P. KEMP 0
0 USDA-Agricultural Research Service, Bee Biology and Systematics Laboratory , Logan, UT 84322-5310 , USA
1 Biology Department, Utah State University , Logan, UT 84322-5310 , USA
- Osmia cornuta adults require exposure to wintering temperatures followed by incubation in the spring to emerge. We studied winter survival, weight loss, emergence time, and post-emergence longevity in O. cornuta exposed to a variety of pre-wintering and wintering treatments. Few bees emerged after exposure to wintering durations <30 days. Maximum survival and longevity were obtained with wintering durations of 90-150 days. Time to emergence following incubation declined with increasing wintering duration and increasing wintering temperature. Pre-wintering treatment had a dramatic effect on bee fitness. Bees pre-wintered for 15 days lost less weight, had higher survival and lived longer than bees pre-wintered for 45 or 75 days. In general, larger bees were more likely to survive the winter and lived longer than smaller bees. We discuss the relevance of these results to survival in wild O. cornuta populations and the management of populations used in orchard pollination.
1. INTRODUCTION
Osmia cornuta (Latreille) is a solitary, uni
voltine, spring-flying mason bee distributed
throughout most of central and southern
Europe and parts of the Middle East
(Peters,
1977)
. Adult females are active for
approximately 20 days in the spring, during which time
they build one or more nests in abandoned
beetle burrows in dead timber or vacant nests of
other bees (mainly Anthophora) in clay
embankments. In addition to foraging for
pollen and nectar to provision their nests, females
also collect mud to build cell partitions and to
seal completed nests. Eggs hatch in
approximately one week, immature development
proceeds through the spring-summer period, and
adulthood occurs in late-summer or early
autumn. Eclosed adults remain in their cocoons
through the winter, and emerge the next spring
as temperatures rise. Respirometry studies with
the closely-related species Osmia lignaria Say
(Kemp et al., 2004)
indicate that this winter
dormancy is diapause-mediated
(sensu Tauber
et al., 1986)
. Wintering in the adult stage
appears to be a derived trait within the family
Megachilidae and the genus Osmia
(Bosch
et al., 2001)
, and is probably associated with
the early seasonal activity period of O. cornuta.
Most other Megachilidae winter as prepupae
and adults are active later in the year
(Bosch
et al., 2001)
.
Osmia cornuta is an excellent pollinator of
fruit trees, and has been studied as an orchard
pollinator in several countries
(Asensio, 1984;
Torchio et al., 1987; Krunic et al., 1991; Bosch,
1994a; Maccagnani et al., 2003)
. As a result, its
foraging and nesting behavior are relatively
well known
(Taséi, 1973a; Maddocks and Paulus,
1987; Jacob-Rémacle, 1990; Bosch, 1994b;
Bosch and Blas, 1994a; Vicens and Bosch,
2000a)
, and methods to manage O. cornuta
populations have been developed, including
preferred nesting materials and nesting cavity
sizes, releasing methods, and number of bees
required per orchard area
(Bosch, 1994b, c,
1995; Vicens and Bosch, 2000b)
. There is,
however, much less information available on
the developmental biology and wintering
requirements of O. cornuta populations
(Taséi,
1973b; Bosch and Blas, 1994b)
. Previous
studies indicate that winter survival in O. cornuta
from NE Spain is high (> 95%) when bees are
artificially wintered (3–5 ºC) for a period of
100–120 days, beginning in October to
earlyNovember
(Bosch, 1994a; Bosch and Blas,
1994b)
. Populations artificially wintered later
in the year (late-November) for shorter periods
(75 days) have lower winter survival (< 86%)
(Bosch, 1994a, 1995)
. Some bees from the
latter populations actually survive the winter, but
are not vigorous enough to chew their way out
of their cocoons the following spring
(Bosch,
1994a)
. These results suggest a strong effect of
pre-wintering periods (defined as the period
from adult eclosion to initiation of wintering)
and/or wintering periods (period from
initiation of wintering to spring incubation) on O.
cornuta survival and vigor. Previous studies
also demonstrate a strong effect of wintering
periods on emergence time. Bees wintered for
75 days have protracted emergence periods
following spring incubation (exposure to warm
temperatures that elicit emergence) compared
with bees wintered for longer periods
(Bosch
and Blas, 1994b)
. To our knowledge, there is
no information available on the effect of
different wintering temperatures on emergence in
this species.
The objective of this study was to investigate
the effect of pre-wintering and wintering
duration and temperature on O. cornuta survival,
emergence tim (...truncated)