Insect feeding systems

The three salient features of feeding behaviour are food choice, mode of feeding, and feeding rate. In this section we discuss the mode of feeding, whereas feeding rate and food choice are considered in more detail in Chapters 5 and 7, respectively. Insects use one of two modes of feeding they either bite off and chew their food,17 or imbibe liquid nourishment.92 Biting-chewing insects, known as mandibulates, possess the ancestral and more general type of mouthparts. There are three pairs of...

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Show a preference for young growing leaves, whereas, overall, larvae of polyphagous species prefer mature leaves of their various host plants. Young leaves are generally more nutritious,107 but at the same time often also contain higher levels of toxic secondary plant substances than mature leaves.14 Specialized detoxification systems are required to compensate for this drawback. These three trends are most probably not fortuitous correlations but reflect some biological principles. Perhaps the...

Signal transduction

There is rapid progress in our understanding of the signal transduction that leads from herbivory or wounding to induced chemical changes. Several researchers, however, have shown that phytochem-ical induction is stimulated more intensely and more specifically by insect secretions, indicating that 'somehow trees can distinguish between sterile scissors and caterpillar mouthparts'.124 The differential effect of herbivore damage and mechanical damage can be explained by herbivore-derived...

Leaf surface chemistry

The first physical contact between an insect and a plant occurs when the insect lands or otherwise touches the leaf surface. Chemical characteristics of the plant surface, in addition to its physical features as discussed in Chapter 3, affect the insect's subsequent behaviour (see Chapter 7). Therefore, leaf surface chemistry merits special attention. The surface waxes or resins constitute the first line of plant resistance. The structural as well as chemical composition of the epicuticular wax...

Plant structure the solidity of antiherbivore protection

3.1 Insect feeding 3.2 Leaf surface 3.2.1 Epicuticular 3.3 Leaf toughness 3.3.1 Mandible 3.3.2 C3 and C4 3.4 Structures involved in mutualistic 3.5 Plant 3.6 Plant 3.8 References A clear understanding of insect-plant relationships requires fairly detailed knowledge of plant structures and chemicals involved in resistance to most insects and susceptibility to others. The present chapter deals with the morphological (physical) factors that interfere with feeding or oviposition, and Chapter 4...

Secondary plant substances

Secondary plant substances can be defined as 'plant compounds that are not universally found in higher plants, but are restricted to certain plant taxa, or occur in certain plant taxa at much higher concentrations than in others, and have no (apparent) role in primary metabolism.' Although chemical differences between plant species have been recognized since ancient times, notions of their function developed gradually only during the twentieth century. In a seminal paper Fraenkel stressed the...

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Figure 3.3 Scanning electron micrographs of plant surfaces. (A) Brassica oleracea var. capitata (Brassicaceae). Scale 10 mm. (B) Festuca arundinacea (Gramineae). Adaxial leaf surface, showing epicuticular wax on a cell on the top of an epidermal ridge. The wax crystals are in the form of plates, typical of the crystals formed by long-chain primary alcohols. The crystals stand on edge and are mutually aligned in three preferred orientations at 120 . Scale 2 mm. (C) Cyathodes colonsoi...

Primary plant metabolism

Photosynthesis is the process by which green plants capture solar energy and store this into sugars, the most basic chemical energy source. Part of this energy is used to convert nitrogen to amino acids, the building blocks of proteins. Sugars are also incorporated in the structural elements of cell walls. The greater part of a plant's biomass consists of primary plant substances. Some of them occur in great quantities lignocellulose, for instance, is the most abundant organic polymer on earth....

Herbivorous insects are they plant taxonomists

The phenomenon of host-plant specialization requires that an insect must be able to search for and recognize its specific host even when this plant is growing in the middle of a species-rich vegetation. J.H. Fabre, in one of his famous books on insect behaviour, concluded that ovipositing females possess a 'botanical instinct' that helps them to recognize their host plants.33 This term has also been used in a slightly different connotation to indicate that an oligophagous insect is in some way...

Specialization on plant parts

Insects may consume every anatomical part of plants but, in addition to host-plant specialization, also show specialization with regard to the feeding sites they occupy on their hosts. Insects of a given species rarely thrive equally well on all parts of their host plant. Many caterpillars, beetles, and grasshoppers are leaf foragers (folivores), ingesting relatively large chunks of leaf material. Other insects show more specific needs. Thus, plant-bugs often penetrate epidermal cells and...

Plant galls

Some of the most exquisite modifications of plant shape are caused by galling insects.87,97 A clear-cut definition of plant galls is difficult to formulate, because of their heterogeneity in form and causative organisms. The one given by Redfern,81 however, seems straightforward 'A plant gall is a growth or swelling caused by hypertrophy (enlargement) and or hyperplasy (multiplication) of plant cells, induced by an organism, which provides nutrients food and shelter for that organism' (p. 55)....

Plant chemistry endless variety

4.1 Plant 4.1.1 Primary plant metabolism 4.1.2 Secondary plant 4.3 Terpenoids and 4.7 Leaf surface 4.8 Plant volatiles 4.9 Concentrations of secondary plant 4.10 Production 4.12 Temporal 4.12.1 Seasonal 4.12.2 Day night 4.12.3 Interyear 4.13 Effects of location and 4.13.1 Sun and 4.13.2 Soil 4.14 Induced 4.14.1 Induced direct 4.14.2 Induced indirect 4.14.3 Variation in herbivore-induced 4.14.4 Genomic and metabolomic changes induced by 4.14.5 Systemic 4.14.6 Long-term 4.14.7 Signal transduction...

Genomic and metabolomic changes induced by herbivory

Herbivory can result in tremendous changes in a plant's chemical composition. For instance, a Lima bean plant that is damaged by spider mites emits approximately 30 volatile compounds, especially terpenoids, that are not released by undamaged plants.77 Herbivory, however, results in many more physiological changes than only those related to volatile emission. Genomic analyses have shown that the expression level of many genes is modified in response to herbivory.216 For Nicotiana attenuata it...

Herbivorous insects something for everyone

2.1 Host-plant specialization 2.2 Food-plant range and host-plant range 2.3 Specialization on plant parts 2.3.1 Above-ground 2.3.2 Below-ground herbivory 2.4 Number of insect species per plant 2.5 Herbivorous insects are they plant 2.6 Host plant is more than food plant 2.7 Microclimates around 2.8 Extent of insect damage in natural and agricultural 2.9 Compensation for herbivore 2.10 Conclusions 2.11 References Insects have the most species of any class of organisms on earth and green plants...

References

Abrahamson, W.G., Melika, G., Scrafford, R., and Csoka, G. 1998 . Gall-inducing insects provide insights into plant systematic relationships. American Journal of Botany, 85, 1159-65. 2. Ahman, I. 1985 . Larval feeding period and growth of Dasineura brassicae Diptera on Brassica host plants. Oikos, 44, 191-4. 3. Barbosa, P. 1993 . Lepidopteran foraging on plants in agroecosystems constraints and consequences. In Caterpillars. Ecological and evolutionary constraints on foraging ed. E. Stamp...

Hostplant specialization

One of the most striking features of insect-plant relationships is the high degree of food specialization among herbivorous insects. This phenomenon forms the heart of these relationships, and all discussions in the following chapters are pervaded with this notion. It is therefore useful to consider the degree of dietary specialization or generalization shown by herbivores. Insects that in nature occur on only one or a few closely related plant species are called monophagous. Many...