- Eight strains of housefly, Musca domestica Linn., from two
laboratories were intercrossed to form a stock population. Virgin males and females from the stock were collected, and nine sets, each
consisting of twelve males mated to five females, were successively
done. Pupae weight, adult weight, emergence time and egg production
of the first batch were measured on four male and four female
offspring from each of two dams mated to the same sire.
Analyses of variance and covariance were made, and the heritability
for each trait and genetic and phenotypic correlations among
the traits were estimated.
Heritability estimates of pupae weight and adult weight, 0.32
± 0.24 and 0.34 ± 0.19 respectively, are reasonable considering
that they are growth traits and are comparable with similar estimates
in some other organisms. Heritability of the emergence time, 0.72 ± 0.30, was high. Heritability of egg production was considered
to be zero and was low when compared with estimates of egg production
in the fowl.
Extimates of genetic correlations between pupae weight and
adult weight, between pupae weight and emergence time, and between
adult weight and emergence time were 0.91, 0.50, and 0.62, respectively.
Genetic correlations between egg production and the other
traits cannot be estimated in this experiment. Phenotypic correlations
were 0.86, 0.03, 0.09, 0.05, 0.08, and -0.09 for between pupae
weight and adult weight, between pupae weight and emergence
time, between pupae weight and egg production, between adult weight
and emergence time, between adult weight and egg production, and
between emergence time and egg production, respectively.
Selection index has been proven to be a very effective method in
selection. Selection indexes were:
I = -0.0504Y₁ + 0.7651Y₂ + 0.1969Y₃ + 0.0050Y₄ for all four
I = -0.0438Y₁ + 0.7648Y₂ + 0.1959Y₃ for the first three traits
where Y₁, Y₂, Y₃ and Y₄ denote measurements of pupae
weight, adult weight, emergence time, and egg production,
The findings from this experiment can serve as fundamental information
for subsequent selection studies in this population.