Aphytis

ENEMIES. The most important enemies are the ichneumon wasps of the genera Encarsia [Prospaltella perniciosi] and Aphytis. These small chal-cid wasps were released in large numbers in the 1970s and are still commonly found in orchards. 

Aphytis melinus. citrus and, 73 Apis mellifera. See Honeybees Apium graveolens var. dulce. See Celery... 

Luck, R. F. and H. Podoler, 1985, Competitive displacement of Aphytis lignanesis by melinus the role of host size and female progeny production. Ecology 66 904-913. 

Host recognition by parasitic Hymenoptera also can be a complex process involving a series of behaviors after initial host contact that must be completed in sequence before an egg is laid. One such sequence is illustrated in Figure 5.7, which diagrams the processes by which Aphytis melinus, a parasitoid used for biological control of California red scale, Aonidiella aurantii, first identifies a potential scale insect species as a potentially suitable host, then assesses the individual quality of that host for utilization (Luck et al. 1982). Egg deposition is the final event of a chain of other behaviors that must be completed in sequence. The series can be broken in several placed and restarted, but no steps can be skipped. 

Unlike most other host-parasitoid systems, the system involving Aphytis wasps and their scale host permit complete isolation of external (i.e., surface) cues from internal cues for the assessment of host quality by the wasp. Diaspidid scale insects are protected by a covering of hardened, nonliving material secreted by... 

Figure 5.7. The behavioral sequence exhibited by Aphytis melinus during oviposition. Reprinted from Luck et al. (1982) with permission.

To determine the identity and relative importance of chemical cues from scale covers on host identification and acceptance by Aphytis species, a suitable bioassay was required. The first such bioassay simply involved covers of California red scale washed with various solvents and placed in observations chambers made of glass microscope slides and Plexiglas (Quednau Hiibsch 1964) (Fig. 5.8). This was sufficient to demonstrate the existence of at least one chemical cue (i.e., a relatively polar, water-soluble kairomone) for oviposition. The importance of the chemical cue relative to such physical cues as scale cover size, shape, and color could not be evaluated. Also, in the absence of precise chemical measurements, it was uncertain if simple washing treatments removed all of the native chemical cues. 

Figure 5.8. Schematic diagram of a bioassay arena made of Plexiglas and microscope slides for Aphytis melinus. The parasitoid is introduced into the hole in the top slide, which is then stoppered for the duration of the bioassay. Reprinted from Luck et al. (1982) with permission.

The potential range of chemical cues used by related Aphytis species may be quite broad. Although A. melinus utilizes relatively polar cues for host recognition, oviposition behavior of Aphytis yanonensis is elicited by chloroform-soluble, relatively nonpolar esters of high molecular weight (26-35 carbon atoms) acids... 

Figure 5.9. Aphytis melinus probing a filter paper disk treated with O-caffeoyltyrosine extracted from covers of California red scale.

Baker, J.L. 1976. Determinants of host selection for species of Aphytis (Hymenoptera Aphelinidae), parasites of Diaspine scales. Hilgardia 44 1-25. 

Luck, R.F. N. Uygun. 1986. Host recognition and selection by Aphytis species response to California red, oleander, and cactus scale cover extracts. Entomol. Exp. Appl. 40 129-136. 

Millar, J.G. J.D. Hare. 1993. Identification and synthesis of a kairomone inducing oviposition by parasitoid Aphytis melinus from California red scale covers. J. Chem. Ecol. 19 1721-1736. 

Takahashi, S., M. Hajika, J. Takabayashi M. Fukui. 1990. Oviposition stimulants in the coccoid cuticular waxes of Aphytis yanonensis DeBach and Rosen. J. Chem. Ecol. 16 1657-1665. 

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