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The exhaustion of food resources which occurs during the ontogenetic growth of Ascia monuste orseis (Godart) results in the dispersion of older larvae to nearby plants in order to complete their development, which might expose these animals to the nutritional variation of the hosts found. This study aimed to verify whether the food ingested in the beginning of the development influences the larvae host preference and whether the shift to a new host can affect the digestion and performance of A. monuste orseis, using two natural hosts: kale (Brassica oleracea var. acephala) and rocket (Eruca sativa), or kale and cabbage (B. oleracea var. capitata). Larvae were reared throughout their larval development on a single host or on two different hosts. When a host change was tested, larvae were reared for four instars on a host, and offered the other host plant in the fifth instar. Development time, percentage of pupation and emergence, pupal weight, fecundity and digestive indices were evaluated. The change in feeding preference for kale and for rocket in the fourth instar, when those were the original hosts, respectively, shows that prior experience plays a major role in food preference of immature A. monuste orseis. The shift can be beneficial for larval development, depending on the order of the hosts; in general, larvae fed on kale at the end of the development showed better performance. Our results presented strong evidence of a considerable phenotypic plasticity in A. monuste orseis for host preferences.

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The aim of the present study was to investigate the effects of different artificial diets, in which sucrose and brewer's yeast were offered separately (food-pair treatment) or mixed (single-food treatment), on the regulation of nutrient ingestion and the performance of wild adult females of Anastrepha obliqua. The amount of diet consumed by females of A. obliqua increased as the concentration of yeast in the diet increased, revealing a phagostimulant effect of yeast. The amount of sucrose ingested was constant in all groups, showing that these flies regulate the ingestion of sucrose. Longevity and production of eggs/female were similar in both groups. Our results suggest that A. obliqua females regulate the ingestion of nutrients to obtain an adequate performance. Dietary self-selective behavior was more efficient for the females of A. obliqua than feeding on a single-food, because the self-selecting flies ingested less food and had a similar performance as the ones fed on the single-food treatment.

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Experiments were performed on adult wild Anastrepha obliqua females to (I) determine whether there is a critical period during the reproductive phase when the absence of protein in the diet impairs egg production; (II) determine whether the females are able to self-select an optimal diet; and (III) determine the discrimination threshold for protein in newly emerged females as well as in 10-day old females that had either been deprived of protein or not deprived. The results showed that protein ingestion is essential during the preovipositing phase to allow egg production, that females are self-selective and that this behavior changes with age according to the reproductive status, and that protein deprivation strongly alters the discrimination threshold for protein. Newly emerged females have discriminatory thresholds similar to protein-deprived insects.

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Experiments were conducted to determine the performance and host preference of Ascia monuste using kale (Brassica oleraceae, var. Acephala) and mustard (B. juncea). These plants differ significantly in water and nitrogen content, with mustard having larger amounts of water and kale larger amounts of nitrogen. The performance results confirmed that kale is a better food source than mustard for the species, even when eggs were collected on mustard leaves in the field. However, when eggs were collected on mustard, the kale nutritive value was lower than the nutritive value obtained when eggs were collected on kale leaves. Furthermore, the results of oviposition preference obtained in the field and in the laboratory have shown a preference for kale, indicating the presence of a positive correlation with performance. In contrast to the data about oviposition preference, there was no immature feeding preference. These results indicate that host selection occurs during the oviposition process. Furthermore, it is possible that the high abundance of kale cultivated in the region studied and the nutritional quality of this plant are two factors that influence the positive relationship between oviposition preference and performance for A. monuste.

RESUMEN

1. Diets containing different amounts of an amino acid mixture were tested in terms of egg production and layings by Ceratitis capitata. The amino acid composition of the diet was identical to that of casein. The other components of the diet were: 1.0 g agar, 0.8 g of a salt mixture, 0.8 g of a vitamin mixture, 1.6 g corn oil, 0.2 g Tween 80, 0.5 ml propionic acid, 90 ml distilled water and 0.5 ml of a 20% alcohol solution of nipagin. Diets containing 0.4, 0.8, 1.2, 1.6 and 2.0 g of an amino acid mixture per 100 ml diet and an amino acid-free control diet were used. The diets were made isocaloric by adding 12.4, 12.0, 11.6, 11.2 and 10.8 g sucrose, respectively. 2. The diet containing 1.2 g amino acids proved to be the best, leading to 6.84 egg layings per female per day and to production of 7.72 eggs per female per day.

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1. Diets containing different amounts of an amino acid mixture were tested in terms of egg production and layings by Ceratitis capitata. The amino acid composition of the diet was identical to that of casein. The other components of the diet were: 1.0g agar, 0.8g of saalt mixture, 0.8 g of a vitamin mixture, 1.6g corn oil, 0.2g Tween 80,05 ml propionic acid, 90 ml distilled water and 0.5 ml of a 20% alcohol solution of nipagin. Diets containing 0.4, 0.8, 1.3, 1.6 and 2.0g of an amino acid mixture per 100 ml diet and an amino acid-free control diet were used. The diets were made isocaloric by adding 12.4, 12.0, 11.6, 11.2 and 10.8g sucrose, respectively. 2. The diet containing 1.2g amino acids proved to be the best, leading to 6.84 egg layings per female per day and to production of 7.72 eggs per female per day

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