Preface. 1. Introduction. 2. Feeding Behaviour and Food Quality. 3. Host Specificity and Speciation. 4. Size. 5. Resource Tracking: Mechanism - Cyclical Parthenogenesis. 6. Resource Tracking: Mechanism - Polyphenism. 7. Resource Tracking in Time. 8. Resource Tracking in Space. 9. Population Dynamics. 10. Community Structure and Species Diversity. 11. Epilogue. References. Index.

Aphid Ecology An optimization approach

The factors responsible for determining the host-plants and feeding sites of aphids, and the various probing activities (the role of the labium, stylet insertion, surface saliva deposition, the behaviour of the aphid, virus transmission) are examined. There is a brief review of stylet structure and movement and the possible sensory nature of these organs, followed by a detailed review of the characteristics of aphid stylet paths in plant tissues. The penetration of epidermis and vascular tissues is treated separately while that within the intermediate tissues is covered in relation to leaves and stems, roots, trees, galls and excised tissue as well as in separate sections on Aphis fabaeScopoli and Myzus persicae (Sulzer). Stylet destinations and behaviour in the sieve tubes are discussed together with general features such as rate and depth of penetration, guidance to the feeding site, effects of tissue hardness and stylet withdrawal. The ingestion rate of plant sap is reviewed and its constitution and importance examined together with the significance of artificial diets. The salivary secretions including sheaths and tracks, their functions and their role in the transference of material between aphid and host are dealt with. The nature of the physical and internal damage resulting from aphid feeding is briefly covered, and also some plant-insect interrelations. The aphid species whose stylets have been examined in plant tissue are listed.

Plant penetration by feeding aphids (Hemiptera, Aphidoidea): a review

Intensive agricultural practices drive biodiversity loss with potentially drastic consequences for ecosystem services. To advance conservation and production goals, agricultural practices should be compatible with biodiversity. Traditional or less intensive systems (i.e. with fewer agrochemicals, less mechanisation, more crop species) such as shaded coffee and cacao agroforests are highlighted for their ability to provide a refuge for biodiversity and may also enhance certain ecosystem functions (i.e. predation). 2. Ants are an important predator group in tropical agroforestry systems. Generally, ant biodiversity declines with coffee and cacao intensification yet the literature lacks a summary of the known mechanisms for ant declines and how this diversity loss may affect the role of ants as predators. 3. Here, how shaded coffee and cacao agroforestry systems protect biodiversity and may preserve related ecosystem functions is discussed in the context of ants as predators. Specifically, the relationships between biodiversity and predation, links between agriculture and conservation, patterns and mechanisms for ant diversity loss with agricultural intensification, importance of ants as control agents of pests and fungal diseases, and whether ant diversity may influence the functional role of ants as predators are addressed. Furthermore, because of the importance of homopteran-tending by ants in the ecological and agricultural literature, as well as to the success of ants as predators, the costs and benefits of promoting ants in agroforests are discussed. 4. Especially where the diversity of ants and other predators is high, as in traditional agroforestry systems, both agroecosystem function and conservation goals will be advanced by biodiversity protection.

http://orton.catie.ac.cr/repdoc/A3596i/A3596i.pdf

Biodiversity in tropical agroforests and the ecological role of ants and ant diversity in predatory function

Publisher Summary The xylem and phloem tissues of plants represent substantial nutrient resources for biophages. The vascular plants, which parasitize xylem are in many respects nutritionally similar to the shoot of the host. Acquisition of xylem sap, containing the water needed for transpiration and growth and the soil-derived elements needed for growth, involves the parasite in having a more negative water potential than the host. Xylem-feeding insects obtain xylem sap by inserting their stylets into a xylem element and sucking out the sap. The thermodynamic limit on xylem sap extraction corresponds to a tension of 3 MPa. Phloem-feeding insects obtain phloem sap by inserting their stylets into the phloem—the phloem turgor pressure drives sap into the insect's gut. By contrast to xylem-feeding heterotrophs, the phloem-feeders have organic carbon in excess of other dietary requirements, such as nitrogen, in phloem the sap. A problem, which phloem-feeders share with less-specialized phytophages is that the nitrogen/carbon ratio is sub-optimal for their growth—they must ingest an excess of organic carbon to obtain sufficient nitrogen.

Phytophages of Xylem and Phloem: a Comparison of Animal and Plant Sap-feeders

Aphids are plant sucking bugs which occur throughout the world. The greatest number of species are in the temperate regions, where few higher plants are free from aphids. They differ from other plant sucking bugs of the Aphidoidea in that the females of at least a few generations are parthenogenetic and viviparous. Although many species are small and inconspicuous, they frequently become abundant. As many as 2000 million per acre (0.4 ha) may live on the above-ground parts of plants, and the roots may support a further 260 million (46, 92, 117, 148). Aphids, like many other insects, are capable of migrating great distances (up to 1300 km) by means of wind (25, 48, 70). Polymorphism is characteristic of aphids. Asexual aphids of some species can either possess wings (in which case they are termed alatae), or lack wings (these morphs are called apterae). Typically there are several structurally different morphs in a species, including both sexual and asexual forms.

Aphid ecology: life-cycles, polymorphism, and population regulation.

The Role of Aphids in Wood Formation. II. The Effect of the Lime Aphid, Eucallipterus tiliae L. (Aphididae), on the Growth of Lime, Tilia x vulgaris Hayne

A. F. G. Dixon

Papers

The Role of Aphids in Wood Formation. II. The Effect of the Lime Aphid, Eucallipterus tiliae L. (Aphididae), on the Growth of Lime, Tilia x vulgaris Hayne