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affected by the split, so one can use the height of the last instar head capsule to indicate
growth during the last instar. The following formula was used to calculate growth rate:
Growth rate = (In (Hf) In (H¡))/t
where Hf is the measurement of the fifth instar head capsule height; H¡ is the
measurement of the first instar head capsule height; and t is the larval developmental
time. A natural logarithm transformation was performed as recommended by LaBarbera
(1989).
Pupae and adult offspring measurement
Each pupa was weighed two days after pupation. Measurements of pupa length
and width also were taken.
For the adult offspring, I recorded the following data: sex, wing length, total body
length (measured from the head to the tip of the abdomen), and fresh weight.
Measurements were made in the afternoon to allow time for the new adults to dry their
wings after emergence. A Vernier caliper (Spi 2000) graduated to 0.1 mm was used for
those measurements. Mass measurements were made with an electro balance. Teneral
butterflies were then stored at -85C for further analysis.
Statistical Analysis
Systat program V 10 was used for the statistical analysis. Since the variation in the
head capsule size between instars w'as large, the measurements were converted to a
logarithmic scale to do the statistical analysis. Repeated measures ANOVA was used for
analyzing growth trajectories between races. The statistical test was performed on both
head capsule width (using the measurement from the first to the fourth instar) and head
capsule height. Since both yielded the same results, I present here the results of the
analysis of head capsule height. Finally ANOVA was used for the rest of the analysis. In