Abstract:
Fruit flies (Diptera: Tephritidae) are among the most notorious pests damaging fruit crops
grown in Tanzania. Demographic and life history parameters of Ceratitis cosyra (Walker)
and Bactrocera invadens (Drew, Tsuruta and White) reared on artificial diet were
investigated at Sokoine University of Agriculture laboratory in 2010. Demographic and
life history parameters of C. cosyra and B. invadens were measured in an environmental
chamber at 25 0 C and 30 0 C with 75% RH to determine pre-adult survival and development
rates, adult survival and fecundity and life history parameters such as the intrinsic rate of
increase, the mean generation time and stable age distribution. The design of the
experiment was split plot arranged in a Complete Randomized Design (CRD) with three
replications. There were two sources of variations: Fruit fly species (being the main-
factor) and temperatures (being the sub-factor). The effect of temperature and species on
eggs laying and survival were tested by two-way analysis of variance (ANOVA). The
Least significance difference (LSD) test was used to identify significant main effects. The
analyses were performed using GenStat package. The results show that B. invadens had
shorter egg incubation time than C. cosyra in all the temperatures tested. Larval and pupal
development rates of B. invadens were significantly faster than those of C. cosyra
independent of temperatures. Life expectancy of male B. invadens was significantly longer
than that of C. cosyra while life expectancy of female B. invadens was higher than that of
C. cosyra, however, the difference was not significant. The average net fecundity was
higher for B. invadens than was for C. cosyra. Both species attained their highest intrinsic
rate of increase and net reproductive rate at 30°C. Furthermore, B. invadens exhibited
higher intrinsic rate of increase and net reproductive rate than C. cosyra at all the
temperatures tested. These findings are useful for improving laboratory-rearing methods,
predicting the fly’s population dynamics, with a view to developing appropriate fly control
and management strategies.
