No abstract

Adult parasitoids depend on sugar‐rich foods such as nectar and honeydew to meet their energy requirements and control insect pests. However, it is poorly known whether parasitoids can detect and feed on honeydew in agroecosystems, where it is the primary carbohydrate source, because this sugar source is less apparent in comparison to nectar and sometimes contains repellent compounds for parasitoids. High‐performance liquid chromatography (HPLC) analyses were carried out to test whether Aphytis melinus DeBach (Hymenoptera: Aphelinidae), a parasitoid whose host does not produce honeydew, feeds on honeydew from non‐hosts. In addition, the correlation between the parasitoid's sugar reserves and honeydew abundance was determined. To do this, both the levels of honeydew producers and the sugar levels of individual collected parasitoids were assessed during different seasons. The overall sugar content was treated as an indicator of energy reserves and the erlose–melezitose ratio as an indicator of honeydew feeding. The data show that A. melinus fed commonly on honeydew from non‐host hemipterans. More than 50% of the female parasitoids collected in spring and summer had recently fed on honeydew and most of them showed a high sugar content. However, in autumn, when the number of honeydew producers was three times lower than in spring and summer, less than 20% of A. melinus were found to have fed on honeydew, with the average total sugar content being reduced by a factor of three. This study demonstrates that A. melinus commonly feeds on honeydew in the field, even though its host does not produce honeydew. The results also suggest that the exploitation of honeydew by A. melinus is a function of the density and species of honeydew producers.

1 The role of ants in the citrus agro-ecosystem is controversial and understanding their ecology may help to clarify their function. The present study determined the daily and seasonal foraging patterns, the spatial distribution, the feeding sources and the associations with honeydew-producing Hemiptera of three ant species that forage in citrus canopies. The dominant ants Pheidole pallidula (Nylander) (Myrmicinae) and Lasius grandisForel (Formicinae) foraged in mutually exclusive territories within the field, although they both shared their territory with the subordinate Plagiolepis schmitzii Forel (Formicinae), a distribution pattern known as 'ant mosaic'. 3 The observed mean overlap for the spatial distribution was significantly lower than the generated by null models, providing strong evidence of spatial interspecific competition, especially between the two dominants. 4 Ants ascended to the canopies from April until November. Colony nutritional requirements and temperature probably shape their seasonal foraging patterns. The daily activity pattern of P. schmitzii was strictly diurnal, whereas L. grandis and P. pallidula were active during the entire day. 5 The ants' diet in the canopies consisted principally of hemipteran honeydew, whereas citrus nectar and predation/scavenging did not represent important food sources. More than 60% of the total honeydew sources and 100% of the citrus mealybug Planococcus citri colonies were tended by ants during spring and summer.

Neoseiulus cucumeris is a predatory mite used for biological control of arthropod pests. Mass-reared predators are fed with factitious prey mites such as Tyrophagus putrescentiae. Although some information on certain endosymbionts of N. cucumeris and T. putrescentiae exists, it is unclear whether both species share bacterial communities. The bacterial communities in populations of predator and prey mites, as well as the occurence of potential acaropathogenic bacteria were analyzed. The comparisons were based on the following groups: (i) N. cucumeris mass-production; (ii) N. cucumeris laboratory population with disease symptoms; (iii) T. putrescentiae pure populations and; (iv) T. putrescentiae from rearing units of N. cucumeris. Only 15% of OTUs were present in all samples from predatory and prey mite populations (core OTUs): the intracellular symbionts Wolbachia, Cardinium, plus other Blattabacterium-like, Solitalea-like, and Bartonella-like symbionts. Environmental bacteria were more abundant in predatory mites, while symbiotic bacteria prevailed in prey mites. Relative numbers of certain bacterial taxa were significantly different between the microbiota of prey mites reared with and without N. cucumeris. No significant differences were found in the bacterial communities of healthy N. cucumeris compared to N. cucumeris showing disease symptoms. We did not identify any confirmed acaropathogenic bacteria among microbiota.

The tomato spider mite Tetranychus evansi Baker and Pritchard (Acari: Tetranychidae), is a worldwide pest of solanaceous crops that has recently invaded many parts of the world. In the present study we examined the ecological impact of its arrival in the Mediterranean region. The spider mite and phytoseiid mite assemblages in various crop and non-crop plants in three areas of Valencia (Spain) were studied a few months before and 10 years after the invasion of T. evansi. According to rarefaction analyses, the invasion of T. evansi did not affect neither the total number of species in the mite community examined (spider mite and phytoseiid species) nor the number of species when the two communities were examined separately. However, after the invasion, the absolute and relative abundance of the native Tetranychus species was significantly reduced. Before the invasion, T. urticae and T. turkestani were the most abundant spider mites, accounting for 62.9 and 22.8 % of the specimens. After the invasion, T. evansi became the most abundant species, representing 60 % of the total spider mites recorded, whereas the abundance of T. urticae was significantly reduced (23 %). This reduction took place principally on non-crop plants, where native species were replaced by the invader. Null model analyses provided evidence for competition structuring the spider mite community on non-crop plants after the invasion of T. evansi. Resistance to acaricides, the absence of efficient native natural enemies, manipulation of the plant defenses and the web type produced by T. evansi are discussed as possible causes for the competitive displacement.