The Holling disc equation (Type-II functional response) for predation, which is mathematically equivalent to the Michaelis–Menten enzyme-kinetics and to the Monod microbial-growth equations, has been used in several linear transformations for parameter estimation. The most commonly used is the Lineweaver–Burk double reciprocal. We compare 4 linearizations of the disc equation and a direct nonlinear fit to stimulated predation data. We conclude that (1) the best parameter estimates are obtained by the direct nonlinear method and (2) the Lineweaver–Burk is the worst of the (all unsatisfactory) linearizations. We propose a new nonparametric technique to use when nonlinear methods cannot be used.

At least two species of Trichogramma (Hymenoptera: Trichogrammatidae) parasitize the eggs of Sepedon fuscipennis Loew (Diptera: Sciomyzidae) in freshwater habitats of central New York. Trichogramma julianoi Platner and Oatman parasitizes S. fuscipennis and Elgiva sundewalli Fries (Diptera: Sciomyzidae). Trichogramma sp. near californicum Nagaraja and Nagarkatti parasitizes S. fuscipennis, E. sundewalli, Tetanocera spp. (Diptera: Sciomyzidae), and pyralid moths (Lepidoptera: Pyralidae). T. julianoi was most active in early and late summer. T. sp. near californicum was most active in mid- and late summer. Another undescribed species, similar to Trichogramma semblidis (Aurivillius), occurs in the same habitats but does not parasitize S. fuscipennis. Its primary hosts are Stratiomyidae (Diptera). Mortality of S. fuscipennis eggs due to Trichogramma varied significantly over the summer and reached 43.6% in late July and early August. A list of parasitoids reared from eggs of insects collected in fresh-water habitats is given.

Eggs of Sepedon fuscipennis (Diptera: Sciomyzidae) < 1, 1–2, 2–3, and 3–4 days old were offered to inexperienced female Trichogramma sp. near californicum in a laboratory experiment. Exposure period (2 h) and number of host eggs offered at one time (10) were held constant. Percentage of hosts parasitized, total number of parasitoid progeny found in a group of hosts, percentage of parasitized hosts yielding adult parasitoids, and survivorship of parasitoid progeny to adulthood all decreased significantly with increased host age. Younger hosts yielded more than one adult parasitoid more often than did older hosts. Over 50% of the adult parasitoids emerging from hosts < 1, or 1–2 days old were female. Hosts 2–3 days old produced only males. The data show a somewhat different relationship of host age to host acceptance and suitability than do some published data on lepidopteran hosts of Trichogramma.