Biology Reference
In-Depth Information
with i ltering hairs that lies between the nectar stomach (crop) and the
midgut (Figure 2.8).
Two physiological mechanisms were found. Only small larvae are
susceptible to invasion by the bacterium. Larvae heavier than about 0.7
milligrams are resistant. Brown's larvae at i rst developed faster, which
allowed them to exceed this minimum quickly, and then slowed devel-
opment so that they were no larger at the end of larval development.
h e brood food produced by Brown's nurse bees contained an antibac-
terial substance that made bacterial spores less likely to germinate and
also had a bactericidal ef ect on vegetative cells.
Tom Seeley and Dave Tarpy tested colonies with multiply and singly
inseminated queens at er they had been inoculated with
P. lar vae
spores. Colonies with multiply inseminated queens had more brood
and larger adult populations and were heavier with stored food than
those with queens inseminated by one male. h ey also had reduced dis-
ease intensity, the number of diseased larvae per comb of brood. Un-
fortunately, this measure confounds the ef ects of polyandry on brood
area with the disease susceptibility of the larvae. h e spread of the
disease could have been equal in the two types of colonies, but the
colonies with more brood distributed over more combs, perhaps a
consequence of polyandry, would have had lower disease intensities
even though they had the same number of diseased larvae. h e multi-
ply inseminated group had signii cantly less variance in disease, which
supports the hypothesis that the trait variation is a consequence of ge-
netic variation, but not the parasite-pathogen hypothesis for the evolu-
tion of polyandry.
Genetic variation was also shown for chalkbrood disease. Inoculated
colonies with multiply inseminated queens had reduced variance in the
prevalence of the disease but did not dif er in their averages. In addi-
tion, colonies were tested for hygienic behavior by using standard
methods. Colonies with multiply inseminated queens had less variance
in hygienic behavior, although the means did not dif er between groups.
An additional study using the same methods, but without inoculating
with pathogens, showed no ef ect of number of queen mates on the
prevalence of sacbrood (a viral disease), American foulbrood, or Euro-
