New Horizons in Insect Science Towards Sustainable Pest Management

Changes in Body Melanisation and Not Body Size Affect Mating Success in Drosophila immigrans 31

and not body size show difference in mated pairs,
ML and CD for light and dark homo-specific
(L × L; D × D) as well as hetero-specific matings
(L × D; D × L) on the basis of contingency χ^2 test
(Table 3 ). By contrast, flies of isofemale lines
varying in body size and not in body melanisa-
tion, under no choice mating conditions, exhib-
ited no difference in mated pairs, ML and CD
(Table 3 ). Thus, laboratory results (similar to
wild data) on dark vs. light isofemale lines show
significant effect of body melanisation on mat-
ing success. By contrast, small vs. large body size
lines did not differ in mating success.

Between and Within Population Variations

Basic data on body melanisation, wing length,

mating latency, copulation duration, ovariole

number and fecundity in a lowland and a high-

land population grown at 21 °C are shown in

Table 4. Variations in these traits show parallel

changes along altitude. There is no difference

for melanisation in each sex. Further, differences

in melanisation (dark and light flies) in both the

populations correspond to changes in reproduc-

tive traits (ML, CD, and fecundity; Table 4 ).

Statistical comparisons show that within popula-

tion differences are quite significant for all traits

Table 1 Field observations on body size and body melanisation in aspirated copulating and noncopulating flies (at
9:00 a.m. daily for 7 days) of D. immigrans. Traits were compared with t test
Day Sex Copulating pairs Noncopulating flies t test b/w
copulant vs. noncopulant
N WL % melanisation n WL % melanisation WL % melanisation
1 M 13 3.57 ± 0.1 1 71.1 ± 3.01 11 3.51 ± 0.10 21.6 ± 2.32 ns
F 3.90 ± 0.13 76.0 ± 4.12 4.01 ± 0.09 27.4 ± 2.10 ns
2 M 7 3.48 ± 0.09 62.4 ± 3.06 9 3.50 ± 0.12 30.2 ± 2.45 ns
F 3.52 ± 0.10 68.2 ± 3.50 3.55 ± 0.1 1 36.4 ± 2.74 ns
3 M 11 3.84 ± 0.14 56.4 ± 2.72 19 3.80 ± 0.13 24.2 ± 2.23 ns
F 3.49 ± 0.08 52.4 ± 3.04 3.46 ± 0.08 29.6 ± 2.15 ns
4 M 12 3.70 ± 0.10 73.5 ± 3.56 6 3.74 ± 0.13 28.2 ± 3.06 ns
F 3.94 ± 0.15 70.4 ± 3.61 3.96 ± 0.15 31.7 ± 2.55 ns
5 M 4 3.85 ± 0.1 1 63.8 ± 3.79 8 3.89 ± 0.10 27.6 ± 2.41 ns
F 4.08 ± 0.09 69.2 ± 3.20 4.00 ± 0.09 33.1 ± 2.50 ns
6 M 14 3.26 ± 0.13 61.2 ± 3.15 7 3.21 ± 0.12 34.0 ± 3.02 ns
F 3.77 ± 0.12 64.3 ± 3.98 3.83 ± 0.1 1 37.5 ± 2.86 ns
7 M 21 3.69 ± 0.09 74.3 ± 3.10 15 3.76 ± 0.13 28.3 ± 2.91 ns
F 4.02 ± 0.07 75.0 ± 2.09 4.07 ± 0.12 32.9 ± 2.46 ns
ns nonsignificant, M male, F female, WL Wing Length, b/w Between
***p < 0.001

Table 2 Data on mating related traits in wild-caught copulating flies of D. immigrans in early- vs. late-mating propen-
sity (MP) groups
Traits Sex Early MP Late MP t test
Wing length (mm) M 3.25 ± 0.09 3.26 ± 0.1 1 ns
F 3.57 ± 0.10 3.54 ± 0.12 ns
Melanisation (%) M 71.0 ± 3.20 32.1 ± 2.41
F 75.8 ± 3.37 36.3 ± 2.60
Mating latency (min) – 7.21 ± 3.46 21.0 ± 3.02
Mated pairs (%) – 67.4 ± 1.42 32.5 ± 1.16
Copulation duration (min) – 64.2 ± 3.75 41.1 ± 3.51
Fecundity (no. of eggs/day) – 59.5 ± 2.88 40.7 ± 2.19
ns nonsignificant, M male, F female
***p < 0.001