The population ecology of Phyllotreta cruciferae Goeze, a flea beetle which is an important pest of cole crops (Brassica oleracea) in central New York was studied in experimental gardens of differing vegetational diversity over a three year period. Adult beetles were more abundant on collards (B. oleracea var. acephala) grown in monocultures than on those grown adjacent to natural vegetation. The emergence of individuals forming the new annual generation was also greater in the pure stands. Predators and parasites appeared to have a negligible influence on the adult beetles in both habitats. Further experiments demonstrated that monocultures were colonized more rapidly and experienced greater feeding damage than stands in which collards had been interplanted with tomatoes and tobacco. Choice experiments in the laboratory showed that chemical stimuli given off by non-host plants (tomato, Lycopersicon esculentum, and ragweed, Ambrosia artemisiifolia) interfered with the host finding and feeding behaviour of P. cruciferae. These results indicate that vegetational diversity can exert a direct influence on populations of phytophagous insects.We conclude that the environmental capacity (Determination in Schwerdtfeger's terminology) of diverse natural communities is lower than that of natural or man-made monocultures. The "associational resistance" resulting from the higher taxonomic and microclimatic complexity of natural vegetation tends to reduce outbreaks of herbivores in diverse communities.

The influence of vegetational diversity on the population ecology of a specialized herbivore, Phyllotreta cruciferae (Coleoptera: Chrysomelidae).

The plant-based resource units insects use for refugia, mating sites, and food vary in two fundamental ways. First, their distributions in time and space are usually patchy, as plants themselves assume distributions dictated by the patchiness of suitable soils and growing conditions. Second, the resources offered by plants vary qualitatively as judged by relative contributions to the fitness of the individual user. As one example, trees with rough rather than smooth bark promote higher survival of gypsy moth larvae (Lymantria dispar) (Campbell et al., 1975; Barbosa, 1978), while larvae fed on white and red oak foliage experience greater survival, develop more rapidly and produce more fecund adults than do those fed on the foliage of most other tree species (Hough and Pimentel, 1978; Barbosa, 1978). The quality of resources offered by a given plant varies widely with factors such as plant tissue, growth stage, and plant nutritional states (see Scriber, Chapter 7).

Finding and Accepting Host Plants

Gustatory receptors associated with feeding in phytophagous insects are broadly categorized as phagostimulatory or deterrent. No phytophagous insect is known that tastes all its essential nutrients, and the ability to discriminate between nutrients is limited. The insects acquire a nutritional balance largely "adventitiously" because leaves have an appropriate chemical composition. Sugars are the most important phagostimulants. Plant secondary compounds are most often deterrent but stimulate phagostimulatory cells if they serve as host-indicating sign stimuli, or if they are sequestered for defense or used as pheromone precursors. The stimulating effects of chemicals are greatly affected by other chemicals in mixtures like those to which the sensilla are normally exposed. Host plant selection depends on the balance of phagostimulatory and deterrent inputs with, in some oligophagous and monophagous species, a dominating role of a host-related chemical. Evolution of phytophagy has probably involved a change in emphasis in the gustatory system, not fundamentally new developments. The precise role of the gustatory systems remains unclear. In grasshoppers, it probably governs food selection and the amounts eaten, but in caterpillars there is some evidence that central feedbacks are also involved in regulating the amount eaten.

Contact chemoreception in feeding by phytophagous insects.

Certain chemicals of plant origin may inhibit food intake in phytophagous insects. Such antifeedants act at low concentrations and are perceived by specialized deterrent receptors or by their modifying effect on normal chemosensory input. In some cases habituation to the presence of antifeedants occurs. When we want to find more chemicals which fulfill all requirements of true and effective antifeedants more research on plant chemistry and insect behaviour is needed. Large scale application only becomes feasible when a number of biological as well as technical problems will be solved.



RESUME

Aspects biologiques des phagodissuadants



Certaines substances d'origine vegetale peuvent inhiber la prise de nourriture par les insectes phytophages. De tels phagodissuadants agissent a de faibles concentrations et sont percus par des recepteurs specialises aux dissuadants, ou par leur effet modificateur sur les entrees d'informations chimiques. Dans quelques cas il se produit une habituation a la presence de phagodissuadants. Pour parvenir a trouver plus de substances chimiques qui reunissent toutes les exigences de veritables phagodissuadants efficaces, il faut plus de recherches sur la chimie vegetale et le comportement des insectes. Des applications a grande echelle ne deviendront possibles que quand de nombreux problemes, tant biologiques que techniques, auront ete resolus.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1570-7458.1982.tb03119.x

Biological aspects of antifeedants

/pdf/dynamics-of-feeding-responses-in-pieris-brassicae-linn-as-a-52lia2vq8r.pdf

Dynamics of feeding responses in Pieris brassicae Linn. as a function of chemosensory input : a behavioural, ultrastructural and electrophysiological study

Even the odors of many non-hostplant leaves have a phagostimulative function besides attraction for the silkworm, Bombyx mori. Consequently, the odor by itself emanating from any plant leaves can not give a significant cue for discriminating acceptable plants from non-acceptable ones. Finding of plant leaves from a certain distance and stimulation of feeding by odors were achieved through the functions of olfactory receptors in the antenna and maxillary palpus, respectively.



The sugar and inositol receptors in the lateral hair and the bitter-substance receptor in the medial hair on the maxilla play relatively important roles in the response to various plant juices. The response pattern of these three receptors roughly correlates with the feeding response.



The maxillary palpus has chemoreceptors which are sensitive to some olfactory and gustatory stimulants such as n-butyl propionate, morin, β-sitosterol, etc. and in addition, it exerts an inhibitory influence upon feeding unless the amount of feeding stimulants in the diet reaches a certain sufficient level.



In addition to synergistic interactions at the receptor sites, which were previously reported for the responses of the bitter-substance and salt receptors in the maxilla, antagonistic interactions were also observed. Some constituent occurring in Artemisia vulgaris leaves, of which the active principle was not identified chemically, was found to inhibit specifically the maxillary sugar receptor activity.



The feeding response is influenced considerably by the amounts or ratios of the feeding stimulants. Accordingly, synergistic or antagonistic interaction of the mixture of chemical stimuli, rather than individual stimuli, is a significant determinant of the palatability of the diet.



Compared with Hyphantria cunea, the feeding behavior of Bombyx is characterized especially by the high sensitivities for many kinds of feeding deterrents associated with various non-hostplants.



ZUSAMMENFASSUNG

CHEMOSENSORISCHE GRUNDLAGEN DER WIRTSPFLANZENWAHL BEIM SEIDENSPINNER



Neben der Anlockwirkung hat sogar der Geruch vieler Nicht-Wirtspflanzen-Blatter auch eine frasanregende Wirkung fur die Raupen des Seidenspinners, Bombyx mori. Infolgedessen kann der von irgendwelchem Laub ausgeschiedene Duft selbst keinen signifikanten Aufschlus fur die Unterscheidung von annehmbaren und abzulehnenden Pflanzen liefern. Das Auffinden der Pfianzenblatter aus einer gewissen Entfernung und die Frasstimulation durch Geruchsreize werden mit Hilfe von olfaktorischen Rezeptoren gewahrleistet, die in den Antennen bzw. den Maxillarpalpen liegen.



Die Zucker- und Inositol-Rezeptoren im Lateralhaar und der Bitterstoff-Rezeptor im medialen Haar der Maxille spielen eine relativ wichtige Rolle bei der Reaktion auf verschiedene Pflanzensafte. Die Reaktionsmuster dieser drei Rezeptoren stehen grob mit der Frasreaktion in Beziehung.



Der Maxillartaster besitzt Chemorezeptoren, die fur einige Duft- und Geschmacksstimu-lantien wie n-Butylpropionat, Morin, β-Sitosterol usw. empfindlich sind, und auserdem eine Funktion, die dann eine Hemmung auf das Fressen ausubt, wenn die Frasstimulantien in der Nahrung keine genugend hohen Betrage erreichen.



Zusatzlich zu den synergistischen Wechselwirkungen auf Seiten der Rezeptoren, uber die fruher als Reaktionen der Bitterstoff- und Salz-Rezeptoren in der Maxille berichtet wurde, wurden auch antagonistische Wechselreaktionen beobachtet. Ein in Artemisia vulgaris-Blattem auftretender Bestandteil, dessen aktives Prinzip chemisch nicht identifiziert wurde, erwies sich als spezifischer Hemmer der maxillaren Zucker-Rezeptor-Aktivitat.



Die Frasreaktion wird betrachtlich durch die Menge und den Anteil der Frasstimulantien beeinflust. Dementsprechend ist die synergistische oder antagonistische Wechselwirkung eines Gemisches chemischer Reize eher fur die Annahme einer Nahrung ausschlaggebend als der einzelne Reizstoff.



Verglichen mit Hyphantria cunea ist das Frasverhalten von Bombyx besonders durch die hohe Empfindlichkeit gegenuber vielerlei Arten von Frasabschreckstoffen gekennzeichnet, die bei verschiedenen Nicht-Wirtspflanzen auftreten.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1570-7458.1969.tb02552.x

Shigeo Ishikawa

Papers

Chemosensory basis of hostplant selection in the silkworm

The Spectral Sensitivity and the Components of the Visual System in the Stemmata of Silkworm Larvae, Bombyx mori L. (Lepidoptera : Bombycidae)

Responses of the chemoreceptors of maxillary sensory hairs in a“Non-preference”mutant of the silkworm

Tactile sense organs on the head of silkworm larva (Bombyx mori)

Some Aspects of Food Preference in Silkworm Larvae, Bombyx mori L. : Lepidoptera : Bombycidae