Juvenile Hormone and host-plant colonization by the black bean aphid, Aphis fabae

Abstract Host-plant colonization by winged, summer forms of Aphis fabae Scop, involves the resumption of embryogenesis and larviposition, leading eventually to flight muscle degeneration. Topical application of Juvenile Hormone I to young adults which (a) had access to the host plant, (b) were starved, (c) were starved and treated with precocene III, or (d) were decapitated shortly after the final ecdysis suggests that embryogenesis and flight muscle histolysis may be stimulated by an increase in Juvenile Hormone titres after settling. The duration of the pre-reproductive period and the initial reproductive rate were not significantly affected, possibly because other neuroendocrine factors are involved in parturition.     

Schellackia occidentalis n.sp., a Blood-inhabiting Coccidian Found in Lizards in Southern California

SUMMARY. Schellackia occidentalis n. sp., is described from the following lizards from southern California: Sceloporus occidentalis becki, S. o. biseriatus , and Uta stansburiana hesperis. Evidence is presented to show that lizards become infected by ingestion of the lizard mite Geckobiella texana. The mite acts as a passive vector by swallowing infected erythrocytes. After ingestion of the mites carrying parasitized red cells, the lizard is infected by migration of the sporozoites into the lizard's intestinal epithelial cells. Schizogony and sporogony occur in the intestinal wall of the lizard. Sporozoites appear in the peripheral blood from 30 to 45 days after ingestion of infected mites. This is the first species of the genus Schellackia to be described in the Western Hemisphere.     

Flight behaviour of the black bean aphid, Aphis fabae, and the cabbage aphid, Brevicoryne brassicae, in host and non-host plant odour

Abstract. Walking alate virginoparae of Brevicoryne brassicae (L.) and Aphis fabae Scopoli were presented with odours of steam-distilled extracts of the non-host plants summer savoury ( Satureja hortensis L.) and tansy ( Tanacetum vulgare L.) in an olfactometer. No effects of the extracts were observed on B. brassicae. However, A.fabae were repelled by summer savoury and tansy odour; both extracts also masked an attractant response to bean (host plant) odour. In a flight chamber, air permeated with odour from host or non-host plants was blown over flying alates of both species, with a green, plant-mimicking target presented once a minute. The incidence of targeted (host-responsive) flight of B.brassicae was not affected by odour from a growing host plant ( Brassica oleoracea ) or a non-host plant tansy. Host plant ( Vicia faba ) odour did not affect the initial rate of climb or the incidence of targeted flight of A.fabae , but when the bean odour was alternated with odour from non-host tansy plants a greater number of targeted flights occurred in the host plant odour. The volatile extracts of tansy and summer savoury were also presented to flying A.fabae. Aphids flying in air permeated with tansy odour at 450g plant equivalents initiated fewer targeted flights than when flying in clean air. However, no differences in flight behaviour were observed with summer savoury extract. In a horizontal wind tunnel the tansy extract at 90 g plant equivalents blown across the surface of yellow targets reduced the numbers of alate A.fabae landing. The results indicate that plant odours can affect flight and landing of aphids.     

Odour‐mediated orientation behaviour of the lily beetle Lilioceris lilii

The lily beetle Lilioceris lilii (Scopoli) (Coleoptera: Chrysomelidae) feeds on Lilium, Fritillaria and Cardiocrinum plants and is a serious pest in gardens and amenity plantings in parts of Northern Europe and North America. In the present study, the odour‐mediated behaviour of L. lilii is investigated by behavioural bioassays using a linear‐track olfactometer. The behavioural responses of L. lilii to hosts and conspecifics are, at least in part, odour‐mediated and the responses differ with respect to the physiological (reproductive) state of the adult beetle (i.e. pre‐ or post‐diapause). Significantly more diapaused female L. lilii move into air streams containing the odour of intact host plants than into clean air, and move into air streams containing odour of host plants and beetles combined in preference to odour from manually‐damaged host plants. Diapaused females also move into air streams containing odours from intact plants over those from larval‐infested plants. Pre‐diapause males move into the air streams of intact plants rather than L. lilii‐infested plants. Pre‐diapause females show no significant response in any experiment. The data indicate that the odour‐mediated responses of L. lilii are consistent with those known for other chrysomelids that produce a male aggregation pheromone to which reproductive individuals of both sexes respond.