Aspects of host—parasitoid interactions of two aphid parasitoids, Aphidius urticae (Haliday) and Aphidius uzbeckistanicus (Luzhetski) (Hymenoptera, Aphidiidae)

Abstract

1. Various aspects were studied of two host-parasitoid interactions: Aphidius urticae parasitizing the cocksfoot aphid Hyabptemides humilis and Aphidius uzbeckistanicus parasitizing the cereal aphid Metopolophium dirhodum The work formed part of a study o n the population dynamics of grassland and cereal aphids in Berkshire, England.2. A.uzbeckistanicus had a higher instantaneous attack rate but a slightly longer handling time than A.urticue. In both cases the functional response was curvilinear. 3.A.urticae was specific to Hhumilis and failed to develop in M.dirhodwn. A.uzbeckistanicus could develop successfully in H-humilis but the functional response was sigmoid and the progeny were less fecund than those reared on the natural host. This species showed a clear preference for M.dirhodum when supplied with mixtures of M.dirhodum and H.humi1is. 4.A.uzbeckistanicus had a faster rate of development and a lower developmental threshold than A.urticae, a situation paralleled by their natural hosts.5. The results are discussed in relation to field observations. A.uzbeckistmicus may have considerable potential for reducing cereal aphid numbers. However, its preference for M.dirhodum mitigates against a reservoir being maintained in the economically unimportant grassland aphid, H. humilis.

Oviposition behaviour ofEphedrus cerasicola [Hym.: Aphidiidae] parasitizing different instars of its aphid host

“…The host is detected by antermal contact, followed by stabbing attacks and/or oviposition, as described for E. cerasicola in the present study (T'Hart et al, 1978 ;Dransfield, 1979 ;Gardner et al, 1984). The host is detected by antermal contact, followed by stabbing attacks and/or oviposition, as described for E. cerasicola in the present study (T'Hart et al, 1978 ;Dransfield, 1979 ;Gardner et al, 1984).…”

“…Short oviposition lasting for about 1 or 2 s is recorded in Aphidius (T'Hart et al, 1978 ;Dransfield, 1979 ;Mackauer, 1983 ;Shirota et al, 1983). Short oviposition lasting for about 1 or 2 s is recorded in Aphidius (T'Hart et al, 1978 ;Dransfield, 1979 ;Mackauer, 1983 ;Shirota et al, 1983).…”

Host instar preference and functional response of Aphidius transcaspicus, a parasitoid of mealy aphids (Hyalopterus species)

“…The leaf petioles were wrapped in wet cotton wool and each leaf was placed on moist filter paper in a petri dish (8.5 cm diameter) with a single female parasitoid. Attack behavior was observed under a binocular dissecting microscope in the laboratory at 20°C, and attack events (potential oviposition events) were distinguished from testing probes by being sustained for 1-2 s as commonly observed for other Aphidius species (' T Hart et al 1978;Dransfield 1979;Mackauer 1983a;Shirota et al 1983). Each experimental female was observed continuously until she had attacked 20 separate aphids.…”

Functional responses to prey density ofEphedrus cerasicola [Hym.: Aphidiidae], an aphidiid parasitoid ofMyzus persicae [Hom.: Aphididae]

“…However such a small experimental area may prevent the manifestation of a sigmoid response (Hassell et aL, 1977 ;'T Hart et al, 1978 ;Luck et al, 1979). Dransfield (1979) demonstrated a sigrnoid response when the parasitoids were exposed to less preferred hosts. Dransfield (1979) demonstrated a sigrnoid response when the parasitoids were exposed to less preferred hosts.…”

“…Among attributes essential for a successful biological control agent are high searching efficiency, ability to aggregate in patches of high host density and rapid reproduction (HasseU, 1978). However, there is increasing evidence that sigmoid response to prey density is quite.common in invertebrates as well (Hassell, 1978 ;Akre & Johnson, 1979 ;Dransfield, 1979 ;Luck etaL, 1979 ;Collins & Dixon, 1981 ;Pandey et al, 1982). Only the sigmoid response is thought to contribute to stability (I-lassell, 1978).…”