Ability of Spalangia endius (Hymenoptera: Pteromalidae) to Parasitize Bactrocera dorsalis (Diptera: Tephritidae) after Switching Hosts

We studied the parasitism capacity of Spalangia endius as a pupal parasite of Bactocera dorsalis after switching hosts. We used pupae of B. dorsalis and M. domestica as the hosts and studied parasitism by S. endius in the laboratory. The parasitism capacities were compared at different host densities and different parasitoid ages. The two functional responses of S. endius fitted a Holling Type II equation. More M. domestica were parasitized than B. dorsalis at all the densities. The ability of S. endius to control M. domestica was α/Th (parasitism capacity) = 32.1950, which was much stronger than that of control B. dorsalis, which was α/Th = 4.7380. The parasitism rate of wasps that had parasitized B. dorsalis had decreased by the emergence time of parasitoids. These results suggest that the parasitoid-pest ratio should be 1:25 to maintain a relatively stable parasitism rate for control of B. dorsalis. The S. endius colony reared on M. domestica successfully controlled a low-density population of B. dorsalis in the lab. We provide evidence suggesting that the parasitism capacity of S. endius needs to be improved.

Discrimination by the Pupal Parasite Spalangia cameroni (Hymenoptera: Pteromalidae) Between Live and Freeze Killed House Fly (Diptera: Muscidae) Pupae

Live house fly pupae were suitable as hosts for Spalangia cameroni Perkins at all age classes tested. However, no parasite emergence occurred from house fly pupae freeze-killed when 12 h old and very limited emergence occurred for pupae freeze-killed when 132 h old. Furthermore, significantly more parasites emerged from hosts that were alive when parasitized when compared with freeze-killed hosts parasitized under similar conditions. In choice experiments, S. cameroni exhibited a strong preference for live hosts over freeze-killed hosts at all parasite-to-host ratios. It does not appear that freeze-killed hosts will be useful as a survey tool or as a method for field propagation of S. cameroni as they are for other species of pteromalids.

NOTE ON CYRTOGASTER VULGARIS WALKER (HYMENOPTERA: PTEROMALIDAE), A SECONDARY PARASITE OF THE ALFALFA BLOTCH LEAFMINER (DIPTERA: AGROMYZIDAE), WITH DESCRIPTIONS OF THE IMMATURE STAGES

Cyrtogaster vulgaris Walker, a pupal parasite of the alfalfa blotch leafminer, Agromyza frontella (Rondani), acts as a secondary agent as well. The adults, which deposit their eggs within host puparia, apparently do not discriminate between healthy leafminers and those parasitized by Dacnusa dryas (Nixon). The egg and larval cephalic structures of C. vulgaris are described and illustrated and the final-instar larval skins of the two parasite species are compared.

Aspects of the biology and behavior of Nesolynx sp. (Hymenoptera, Eulophidae)

This research was carried out to study some aspects of the biology and behavior of Nesolynx sp. (Hymenoptera, Eulophidae), a pupal parasite of Psorocampa denticulata (Lepidoptera, Notodontidae) a defoliating caterpillar of Eucalyptus spp. in Brazil. The adults emerge from the host pupa through a circular hole on Its dorsal region. Mating occurs righ after the emergence and the longevity of adults was two days for the males and four days for the females. Regarding to the host species Diatraea saccharalis showed a number of adults significantly greater than Galleria mellonella and the increasing temperature from 21±1 °C to 26±1°C caused a significative increasing in the number of emerged adults in both host species. The emergence of adults increased proportionally to the period of exposition to the host up to 3.50 days; after that, a considerable decrease in the emergence was observed. The parasitoid showed parthenogenetic reproduction therefore the average number of emerged males was significantly greater than the number of females. The sex ratio was similar for the insects emerged from virgin or mated females (0,96) and the life cycle lenght was around 18.34 days for both conditions.

DISCRIMINATION BY THE PUPAL PARASITE MUSCIDIFURAX ZARAPTOR1 FOR LIVE AND FREEZE-KILLED HOUSE FLY2 PUPAE3

Muscidifurax zaraptor Kogan and Legner was able to discriminate between live and freeze-killed house fly pupae at low parasite-to-host ratios (1:40) and preferred live hosts. As the parasite-host ratio and resulting rates of parasitism increased, a greater preference was shown for live hosts. However, high parasite-host ratios (1:5) where levels of parasitism reached the upper limits in live hosts (65 – 70%), discrimination disappeared suggesting that less suitable freeze-killed hosts were selected as hosts over previously stung but unparasitized live hosts. Freeze-killed house fly pupae may be useful in measuring natural Muscidifurax activity especially during periods of low natural host populations and may provide a ready host source in conjunction with parasite releases.