Patterns of Relationships Between Certain Leafhoppers and Plants. Part Ii. Role of Sensory Stimuli in Orientation and Feeding

Abstract

The orientational and feeding responses of E. devastans are determined by stimuli some of which are unspecific and others specific to the host (cotton) and nonhost (castor) plants. The green colour and humidity stimuli are unspecific and attract the leafhopper equally strongly to both the plants. Their odour is specific to each. The odour of the host (cotton) including that of its constituents camphene and α‐pinene attracts while the nonhost (castor) odour repels the leafhopper. After its arrival, unspecific mechanical contact stimuli elicit the insect's proboscis response, followed by ingestion which is determined by certain unspecific gustatory stimuli e.g., sucrose and glucose. Ingestion is further increased by the specific odour of the host (cotton) but not of the nonhost (castor) plants, resulting in a greater food‐intake from the former. Résumé ASPECTS DES RELATIONS ENTRE CERTAINS JASSIDES ET LES PLANTES. 2ÈME PARTIE—RÖLE DES STIMULI SENSORIELS DANS L'ORIENTATION ET L'ALIMENTATION Les réponses d'orientation et d'alimentation d'E. devastans sont déclenchées par des stimuli dont certains sont spécifiques et d'autres non spécifiques, soit à la plante hôte (coton) soit aux plantes non hôtes (Ricin). Ces stimuli peuvent être perçus à distance et peuvent déclencher l'orientation ou le comportement alimentaire, tandis que d'autres sont perçus par contact et ne déterminent que les seules réponses alimentaires. Parmi les stimuli perçus à distance, les stimuli‐visuels, en particulier la couleur verte et l'humidité (vapeur d'eau) ne sont pas spécifiques; tous les deux provoquent une forte attraction des Jassides. La plus grande attractivité des insectes pour le vert, de préférence à d'autres couleurs, faciliterait la rencontre avec les plantes plutôt que d'autres substrats. Les odeurs de la plante‐hôte (coton) ou de plante non hôte (ricin) sont spécifiques à chacune d'elles. L'odeur du coton comprenant celle de ses constituants camphène et α‐pinène, attire les Jassides, tandis que celles du Ricin les repousse. Cependant ces insectes sont également et fortement attirés par ces deux plantes, sans doute en raison de la faible intensité des stimuli odorants et de l'influence prépondérate de la couleur verte. Après être parvenu sur une plante ou toute autre source alimentaire des stimuli mécaniques de contact non spécifiques provoquent l'extension du rostre quelle que soit la nature chimique du substrat. La réponse du rostre est suivie par l'ingestion de nourriture et d'eau. Certains stimuli gustatifs de l'aliment ingéré par exemple des sucres, conditionnent la quantité absorbée: l sucrose à 0,01 M est le plus stimulant, le glucose l'est moins et le fructose demeure sans action. La quantité de nourriture ingérée est par ailleurs accrue par stimuli de l'odeur spécifique de l'hôte (coton), mais non par celle des plantes non hôtes (Ricin). En conséquence les Jassides prélèvent plus de nourriture aux dépens du coton qu'aux dépens des plantes non hötes.

Potato Leafhopper (Homoptera: Cicadellidae) Varietal Preferences in Edible Beans in Relation to Visual and Olfactory Cues

“…Initially, humidity and visual signals were suggested as distance-stimuli that attract leafhoppers regardless of slight variations among hosts (Saxena and Saxena 1974). Desiccated leafhoppers are more attracted to watered leaves than to wilted leaves and to wet Þlter paper over dry Þlter paper, suggesting that humidity in the vicinity of water sources, including plants, attracts leafhoppers, and their contact with water or plant sap elicits ingestion (Saxena and Saxena 1974).…”

Study on the Role of Olfaction in Host Plant Detection of <I>Scaphoideus titanus</I> (Hemiptera: Cicadellidae) Nymphs

“…The results from behavioral tests indicated a strong attractiveness of grapevine leaves and shoots for the nymphs. We excluded the inßuence of vision in our trials and, although the synergistic role of other kinds of stimuli, such as humidity and CO 2 emission, was not examined in our experiments, their importance has been shown in previous studies on A. devastans (Saxena and Saxena 1974). Furthermore, in the presence of a plant stimulus in the olfactometer, we observed an increase of the number of specimens that made a choice, whereas in its absence, the no-choice option tended to be higher.…”

“…Among the identiÞed compounds, ␣-pinene, rather abundant in the extract, is known to be active (e) sensory cavity type 1; and (f) sensory cavity type 2. FL, ßagellomere; hl, long hair-shaped sensillum; hs, short hair-shaped sensillum; PE, pedicel; sc1, sensory cavity type 1; sc2, sensory cavity type 2. toward the leafhopper A. devastans (Saxena and Saxena 1974). The development of a suitable semiochemical-based tool for S. titanus monitoring would be highly useful, because efÞcient physical and chemical attractants totally lack and the only suitable method for monitoring nymphs is direct Þeld sampling, which requires instructed technicians and is a time-consuming and costly activity.…”

“…Up to now, the role of plant volatiles in host Þnding and selection has been investigated in only a few leafhopper species: Amrasca devastans (Distant) (Saxena and Saxena 1974), Nephotettix virescens (Distant) (Khan and Saxena 1985), Dalbulus maidis (DeLong and Wolcott) (Todd et al 1990), Empoasca fabae (Harris) (Bullas-Appleton et al 2004), and Homalodisca coagulata (Say) (Patt and Sé tamou 2007). Plant odors were recognized to either attract or repel the species and, in some cases, the odors from different varieties showed different attractiveness to the insects (Khan andSaxena 1985, Bullas-Appleton et al 2004).…”

Vegetational designs for insect-habitat management

“…It may also result in less tenure time by the herbivores on the host plants (Risch 1981). Shading by the tall crop can affect the microdimate, and hence insect development, by inhibiting feeding such as in the case of leafhoppers (Saxena and Saxena 1974).…”