Mean Parasitism Rate Research Articles

Parasitism rates in relation to nest site in bees and wasps (Hymenoptera: Apoidea)

To account for differences in occurrence of social behavior in different lineages of bees, Michener (1985) hypothesized that ground nests are more easily located by parasites than are twig nests. In the former case parasites search in two dimensions, while in the latter they search in three-dimensional space. One prediction derived from this hypothesis is that ground nests will have higher rates of parasitism than twig nests. A survey of published reports on rates of cell parasitism for 92 species of nesting bees and wasps (Apoidea) shows no significant differences in mean parasitism rates between these two classes of nests. The analyses were repeated at the generic level (N=44), yielding the same pattern. These data may be biased due to phylogenetic effects. Paired comparisons (n=11 pairs) of related taxa that differ in nest site show that ground-nesting taxa more often have higher rates of parasitism than twig-nesters. The use of artificial “trap-nests” to study twig-nesters significantly enhances the success rate of parasites. This bias, as well as several other limitations, suggests that experimental studies of the host-searching capabilities of parasites and predators may be more efficacious than such comparative tests.

ベトナム北部のイネウンカ類卵期の死亡要因

Mortality factors of eggs of Nilaparvata lugens STAL, Sogatella furcifera HORVATH and Laodelphax striatellus FALLEN on the winter-spring rice crop were studied in the Red River Delta in early April, 1993. Mymarid parasitism was responsible for almost all mortality of the three planthoppers on the winter crop. The mean parasitism rates were 20.6%, 32.8% and 53.2% for N. Lugens, S. furcifera and L. striatellus, respectively. On the other hand, both parasitism (12.2-45.5%) and physiological death caused by rice plant reaction (4.5 - 57.1 %) were important mortality factors of S. furcifera eggs on three varieties of early-spring and spring crops. Physiological egg mortality of S. furcifera colonies originating from populations obtained in the Red River Delta and Chikugo, Japan were high on two japonica varieties (Reiho and Niigatawase) and low on and indica variety (TN 1) and a japonica X indica variety (Saikai 184). The difference in the egg mortality rate on the 4 varieties between the two colonies was insignificant. This gives support for the view that the winter-spring crop in the Red River Delta is a major source of air-born rice planthoppers invading southern China where they multiply and produce ocean-crossing migrants into Japan in the Baiu season.

Mass-rearing Technique for Aleochara bilineata (Coleoptera: Staphylinidae)

Mass-rearing techniques for economic production and storage of large numbers of Aleochara bilineata (Gyllenhal) (AB) for laboratory use and field studies are described. AB adults caged in plastic containers holding 1 cm of moist sand at 14°C, in darkness, readily accepted onion maggot (OM), Delia antique (Meigen), larvae as their food source. AB eggs collected from oviposition cages were distributed around OM pupae scattered over the surface of moist sand in similar tightly sealed plastic containers. At 22°C and a photoperiod of LD 16:8, with 1:1 AB egg: OM pupa, the mean parasitism rate was 71%; larvae reared under these conditions did not enter diapause. At 14°C, in darkness, using 1.25:1 AB eggs: OM pupa reared under diapause-inducing conditions, the mean parasitism rate was 74%, and >95% of the first-instar AB entered diapause. A minimum of 8 weeks at 1°C aws necessary to fulfill diapause requirements; diapausing larvae could be held at this temperature for as long as 6 months with no decrease in survival rate. Five hours of labor per week were required to produce ca. 10,000 AB adults per week.

Experimental parasitization of eggs of Triatoma maculata (Erichson) by the oriental microhymenopteran, Gryon triatomae Masner and comment on the susceptibility of other neotropical triatomines

The oriental microhymenopteran wasp, Gryon triatomae Masner, 1975 was reared in eggs of triatomine bugs, including vectors of Chagas' disease. In particular, G. triatomae was maintained for 31 generations in eggs of Triatoma maculata (Erichson). Only one parasite develops in each bug egg and 30 to 40 days are required for completion of development at 24 ± 1 °C. Mean parasitization rate of 7484 eggs of T. maculata, in 54 rearings, was 34·7% with a range from zero to the highest rate of 86·7%. Mated females produce predominantly female progeny (mean sex ratio, 1 male : 6·7 females). Unmated females produce parthenogenetic males. The wasp reproduces in fertile eggs, from those recently laid to those with well-advanced bug embryos. Infertile eggs are not usually parasitized. Both sexes survive for one to two weeks unfed, but for several weeks (up to 16 for females) if fed (on honey). Frequent ovipositions may reduce survival. Successful parasitization by females persisted for about three weeks but declined subsequently. Abortions of developing Gryon were usually 10% or less. Brief comparison with other neotropical triatomine species indicates that eggs of Triatoma spp. are susceptible to G. triatomae; Panstrongylus spp. seem relatively poor hosts, and there is little or no parasitization of Rhodnius spp.

Euplectrus puttleri 1 Established on the Velvetbean Caterpillar, Anticarsia gemmatalis,2 in Southern Florida3

The euplophid parasite, Euplectrus putlleri Gordh, introduced from Colombia (S.A.) was released in southern (Dade Co.) Florida in 1976 and has become established on Anticarsia gemmatalis (Hubner). Small (< 1 cm) and medium (1–2 cm) larvae were found parasitized and produced an average of 4.4 parasite adults per larva. The mean parasitism rates of small and medium size larvae at one site were 5.0 and 8.9%, respectively. The parasite has survived 3.5 years and spread at least 9.1 km.

The release ofOpius concolor andO. Concolor var.Siculus [Hym.: Braconidae] against the spring generation ofDacus oleae [Dipt.: Trypetidae] on Corfu

Releases ofOpius concolorSzepl. andO. concolor var.siculusMon. were carried out in the spring to determine if they could be used as a biological control agent against the heavy infestation ofDacus oleaeGmel. which occurs on Corfu at that time. At an initial density of 300–400 parasites per tree the mean parasitism rates of 3rd stage larvae ranged from 30–50% in the 1st week following the release, indicating thatOpius could work well in the spring in the tall trees with large numbers of ripe and heavily infested fruits that are found on Corfu.