The mixture of volatile compounds emitted by Brassica oleracea var. sabauda changed significantly in response to feeding and/or oviposition by Murgantia histrionica (Heteroptera: Pentatomidae). Volatiles were collected from (1) healthy plants and those with (2) feeding punctures, (3) a combination of feeding punctures and oviposition, (4) feeding punctures and one hatched egg mass and (5) plants bearing only an egg mass. In the case of plants with feeding punctures or feeding punctures plus an egg mass, the volatiles were also collected at different time intervals after plants were subjected to these two treatments (0-24 h, 24-48 h and 48-72 h). Gas chromatographic and gas chromatograph-mass spectrometric analysis showed that the percent emission of several compounds changed significantly from plants subjected to the feeding and oviposition or just oviposition. Percentage of terpenes generally decreased after feeding and oviposition, although the percentage emission of (E)-β-caryophyllene from these plants and those with just feeding punctures significantly increased. Plants with just an egg mass emitted linalool de novo but not (E)-β-ocimene. The emission of jasmonates, mainly methyl jasmonate, increased from plants with feeding punctures plus an egg mass compared to those with only an egg mass. Higher percentages of the volatile glucosinolate derivatives (VGSs), mainly 4-methoxy-3-indolylacetonitrile, were emitted by plants with feeding punctures and an egg mass. The percentage emission of most of these compounds increased during the first 24 h after the treatment and then decreased over the next 24 h, except for methyl jasmonate, which remained high also 48-72 h later. The possible ecological roles of such volatiles in plant interactions with the second and third trophic levels are discussed.
The aim of this study was to evaluate the effects of different diets on the development and reproduction of Lygus rugulipennis Poppius (Heteroptera: Miridae). Using 2 laboratory generations (F1 and F2) obtained from field-collected L. rugulipennis, the following diets were tested: beans, beans plus Tenebrio molitor (L.) (Coleoptera: Tenebrionidae) pupae, and a commercial artificial diet, which was developed for mass rearing of Lygus hesperus Knight. As oviposition substrates, beans and agar/parafilm rolls were used. Our data show that both the artificial diet and the artificial oviposition substrate were ineffective substitutes for beans for both laboratory generations. Stage-dependent and total survival rates clearly indicated that F1 Lygus bugs survive significantly longer when they are reared on vegetable substrates i.e., beans and beans plus pupae. The differential effects of the diets were more pronounced in the F2 generation, in which the embryonic development was longer for eggs from females reared on the artificial diet than on beans, and in which the second instar nymphs did not survive on the artificial diet. Both the total duration of post-embryonic development and the longevity of F1 males were shorter on the artificial diet than on beans. Female fecundity was affected by diet in terms of total duration of the oviposition period and mean number of eggs laid/female, since these parameters were lower on the artificial substrate, compared with those obtained on the bean substrate. However, the diet did not affect the morphological parameters, as there were no significant variations in weight, width of cephalic capsule, and tibia and hemelytra length. Since L. rugulipennis cannot be reared on the commercially available artificial diet, we discuss the necessity to improve both the artificial diet and oviposition substrate so that this Lygus bug and its specific egg parasitod Anaphes fuscipennis Haliday (Hymenoptera: Mymaridae) can be mass reared.
This paper reports the results of a comparative laboratory analysis of the behavioural responses of the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) to semiochemical cues from four species of pentatomid bugs, Nezara viridula (L.), Eurydema ventrale Klt., Murgantia histrionica Hahn. and Graphosoma semipunctatum F. (Heteroptera: Pentatomidae). In a Y-tube olfactometer, T. basalis was attracted by volatile chemicals from N. viridula, but not from other pentatomid species. In an open arena, the parasitoid reacted to chemical trails left on filter paper by all the species but most intensely to those left by N. viridula. However, upon encountering pentatomid eggs, T. basalis examined more intensely and probed more frequently the eggs of G. semipunctatum than those of the other species. The parasitoid only parasitized and emerged from eggs of G. semipunctatum and N. viridula; those of the other species were unsuitable. Therefore N. viridula is semiochemically confirmed to be a coevolved host (old association) of T. basalis, whereas G. semipunctatum may be a potential non-coevolved host (new association). The utility of these tests for defining a parasitoids' host specificity and in assessing the risk of non-target effects in biological control is discussed.