Let L represent the allele for long wings (dominant) and l represent the allele for vestigial wings (recessive).

i)
Let L represent the allele for long wings (dominant) and l represent the allele for vestigial wings (recessive).

Parental (P) Generation:
Phenotype: Long-winged male $\times$ Vestigial-winged female
Genotype: LL $\times$ ll

Gametes:
L, L $\times$ l, l

F1 Generation:
Genotype: All Ll
Phenotype: All Long-winged

F1 Self-cross:
Phenotype: Long-winged male $\times$ Long-winged female
Genotype: Ll $\times$ Ll

Gametes:
L, l $\times$ L, l

F2 Generation (Punnett Square):

$$\begin{array}{|c|c|c|} \hline \text{Gametes} & \text{L} & \text{l} \\ \hline \text{L} & \text{LL} & \text{Ll} \\ \hline \text{l} & \text{Ll} & \text{ll} \\ \hline \end{array}$$

ii)
The phenotypes of the offspring in the F2 generation are:

• Long-winged
• Vestigial-winged

The genotypic ratio in the F2 generation is:

$$\text{LL} : \text{Ll} : \text{ll} = \boxed{\text{1 : 2 : 1}}$$

iii)
From the F2 Punnett square, the genotype for vestigial wings is ll. There is 1 ll genotype out of 4 possible genotypes.
Percentage of vestigial-winged drosophila flies in the F2 generation:

$$\frac{1}{4} \times 100\% = \boxed{25\%}$$

iv)
Drosophila melanogaster is suitable for heredity experiments due to its short life cycle, allowing many generations to be studied quickly. They produce a large number of offspring, which provides statistically significant data. Their small size makes them easy to handle and maintain in laboratory settings, and they exhibit distinct, easily observable traits for genetic analysis.