Some Experiments On Sex Ratio and Sex Regulation in the Pteromalid Lariophagus Distinguendus

Females of the parasitoid wasp, Dendrocerus carpenteri (Hymenoptera: Megaspilidae), adjust offspring sex allocation when competing for hosts

“…Mated and unmated females were equally likely to encounter an unparasitized host and deposit an egg as well as to re-encounter and reject or, alternatively, accept and superparasitize an already parasitized host. Whereas both kinds of female can alter their offspring allocation in response to patch experience (van den Assem, 1971;Charnov et al, 1981;Suzuki et al, 1984;Cloutier et al, 1991), only mated females can alter offspring sex allocation in response to parasitized and unparasitized hosts. For example, after encountering an already parasitized host or a conspecifi c competitor, a female may place a higher value on the next host she fi nds and deposit a fertilized rather than an unfertilized egg regardless of host quality and oviposition sequence (Chow & Mackauer, 1996).…”

“…Therefore, host-quality models predict that mothers should deposit unfertilized eggs in low-quality and fertilized eggs in high-quality hosts (King, 1993;Godfray, 1994). Host quality is not absolute but relative, depending on the kinds of host available and the female's physiological state (van den Assem, 1971;Cloutier et al, 1991;Mackauer et al, 1996). Having encountered an already parasitized host, a female may place a higher value on the next host she fi nds, regardless of its quality, and deposit a fertilized egg (van den Assem, 1971;Cloutier et al, 1991) or superparasitize it if her offspring is likely to survive larval competition (Mackauer et al, 1992;Visser et al, 1990Visser et al, , 1992Lebreton et al, 2009).…”

Sex ratios in natural populations ofAphelinus mali (Hym.: Aphelinidae) in relation to host size and host density

“…A number of parasitoids, particularly solitary parasitic hymenoptera are known to discriminate between acceptable hosts in the allocation of sexes, laying mostly, male eggs in smaller hosts and mostly female eggs in larger hosts (Chewyreuv, t913;Holdaway & Smith, 1932;Brunson, 1937;Clausen,. 1939 ;van den Assem, 1971 ;Sandlan, 1979). Charnov (1979) proposed an explanation that parasitoid fitness should increase with its size, which in turn should increase with host size.…”

“…In this. context, it is of interest to mention that for some parasitoid species, ovipositing females have been found to judge host size on a relative basis (van den Assem, 1971 ;Charnov et al, 1981 ;Hurlbutt. 1987a) whilst other species seem to judge primarily in absolute terms (Charnov et al, 1981 ;Jones, 1982).…”

Lariophagus distinguendus (Hymenoptera: Pteromalidae) (Förster)—Past, Present, and Future: The History of a Biological Control Method Using L. distinguendus against Different Storage Pests

“…Thus, the objections of Gonen and Kugler could be disposed of. Several other studies were conducted by van den Assem [33,34] and his colleagues Bellows, Charnov, and Werren [35,36,37] and L. distinguendus was established as a model organism for general behavioral, evolutionary, and population ecology. The main focus of their work was on sex-ratio regulation and population dynamics [35,36,37].…”