Virgin females of Lobesia botrana Denis & Schiffermüller were mated at ages of 1, 3, 5, 8, 12 and 16 days and the effect of mating delay on reproductive output assessed. Delayed mating did not affect female mating success but fertilization was reduced in 16-day-old females. Increased mating delays substantially affected daily oviposition pattern and resulted in a significant reduction of both fecundity and fertility, so that mean number of viable eggs laid decreased from 150 to 22 in 1- and 16-day-old mated females, respectively. Heavier females were more constrained than lighter ones by mating delays and female reproductive efficiency (no. viable eggs/female body weight) was also significantly reduced. Female longevity significantly increased and oviposition period gradually declined with mating delay. The number of viable eggs was positively correlated with both female weight and oviposition period; female longevity and female weight were also significantly correlated. However, the significance of these correlations declined with increased mating delay. Results overall indicated that mating delay drastically reduces female L. botrana reproductive output. The implications of delayed mating of females are discussed from an ecological perspective in relation to L. botrana control using mating disruption.
Following the first survey of intraspecific pheromone variability in Ostrinia nubilalis Hbn (ECB) in Europe and North America (K LUN & C OOPERATORS , 1975), the sex attraction responses of male populations of ECB to 3 ratios of the Z : E isomers (97 : 3 , 35 : 65 , 3 : 97) of the 11-tetradecenyl acetate were studied at 28 locations in Europe, 3 in Egypt and one in the Hebei province of the People's Republic of China, during the 1978-1981 period, as a part of the cooperative program of I.W.G.O. (International Working Group on Ostrinia). In the palearctic region, the ECB populations exhibited pheromone polymorphism. The Z phenotype was the only one observed in 13 localities, mainly with low levels of capture. In other places, the two phenotypes Z and E were in sympatry, very often with the presence of their presumed hybrid Z x E, responding to the 35 : 65 Z : E mixture. The survey confirms the great prevalence of the Z phenotype in corn fields all over the world. The E phenotype was prevalent only in 5 locations in northern Italy and southern Switzerland.
The effect of vine phenological stage during larval feeding on the reproductive output of Lobesia botrana (Denis & Schiffermüller) adults was assessed. Larvae were reared under field conditions on vine inflorescences, unripe or ripe berries simulating the first, second and third insect generations respectively. The resulting adults showed significant differences in body weight, longevity and reproductive output as measured by oviposition period, total fecundity and reproductive efficiency (viable eggs/body weight) for females, and spermatophore number and volume of the first spermatophore for males. Viable egg number was positively correlated with female body weight for all treatments but male reproductive efficiency (spermatophores/body weight) was not. The reproductive output of females from larvae reared on a standard semisynthetic diet was comparable to that of females reared on ripe berries whereas males showed a higher reproductive output when reared on semisynthetic diet. These results clearly show that data obtained from insects reared on artificial diet cannot be extrapolated to 'fieldderived' adults. The results suggest that the variation in L. botrana reproductive output due to the larval food source should be taken into account as a potential factor affecting insect population dynamics. It is suggested that different intervention thresholds, such as those based on pheromone catches, may be needed for each of the three moth generations, to compensate for the increased fecundity and potential to cause larger amounts of crop damage of later generations.
Studies of short or medium range geographic variations play an increasing role in ecological genetics, and sensitive techniques are required to detect them. In this respect, two sampling techniques were compared in D. melanogaster. The biological data were provided by the analysis of four natural populations from the same geographic area, Spain (one) and Southern France (three), for four morphometrical traits: abdomen and thoracic pigmentation, and wing and thorax lengths. Traits were measured on wild living females and on their progeny reared in the laboratory at 25 degrees C. For progeny analyses, two techniques were compared: the usual isofemale line technique, sib families issued from a single female, and a new isogroup technique, the progeny produced by a group of 20 wild-collected parents. Large phenotypic variations were observed in wild living flies, corresponding to the unstability of natural environmental conditions during their development. Among laboratory grown flies, variations were much smaller. Between isogroups, differences were small, due to sampling error and some common environment effects. Variations between lines were much greater, thus demonstrating a strong genetic component. When different populations have to be compared, the isogroup technique should be preferred since, for the same amount of work, the lesser variability between groups provides a more precise characterization of the population means.
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