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Laboratory investigations were conducted on the biology of Apanteles subandinus Blanchard and the effect of temperature and relative humidity on its bionomics. Temperature responses of this parasite were compared with those of Apanteles scutellaris Muesebeck and their common host, the potato tuberworm, Phthorimaea operculella (Zeller). Responses of the parasites and their host to physical factors were evaluated by using the intrinsic rate of natural increase (r) as a bioc1imatic index. At 80°F and 50 per cent relative humidity (R.H.) the mean duration of the life cycle of A. subandinus from egg to adult was 15 days; egg, 1 day; first instar, 4.5 days; second instar, 2.5 days; third instar, 2 days; prepupa, 0.5 days; and pupa, 4.5 days. The parasite egg is deposited at random in the body cavity of the host larva where the parasite larva develops. There are three Instars, the first being mandibulate-caudate and the other two' hymenopteriform. The mature larva emerges from the host, killing it in the process, and spins a silverwhite cocoon. There is essentially no preoviposition period in A. subandinus and the parasite is an arrhenotokous species, the virgin female producing only male progency. Between 60 and 90°F, speed of development was directly related to temperature. A constant temperature of 95°F prevented development of the parasite beyond the first insrar. Longevity and reproductive periods were inversely related to temperature, longevity following the pattern of the curve of physiological longevity. Production of progeny was maximum at 80°F. As determined by calculations of the intrinsic rate of natural increase, A. subandinus persisted and increased in numbers between 60 and 90°F. Optimal temperature for the parasite was 85°F. Relative humidity did not affect development. At 80 and 85°F, maximum progeny production occurred at 50 per cent R.H.

The biology of Trichogramma brevicapillum Pinto & Platner (Hymenoptera, Trichogrammatidae) reared on eggs of Trichoplusia ni (Hübner) (Lepidoptera), and the influence of some abiotic and biotic conditions on the parasitization strategy of the adults were studied. Egg, larva, prepupa, and pupa are described. Development of these stages lasted ca. 1,3, 1, and 5 days, respectively, at 25°. Reproduction is biparental, arrhenotokous. The preoviposition period lasts ca. 3 hr, and oviposition activity was maximal in the 3rd and 4th hr of the photophase and was minimal in the scotophase. The suitability of T. ni eggs as a host was maximal in the blastula stage of the embryo, decreased sharply in the early stages of differentiation, and increased rapidly in the later stages of embryological differentiation. A single ♀ reared from a host egg was larger and more fecund than 2 2 from eggs yielding 2 or 3 parasites. Oviposition by individual ♀♀ was restrained when the host egg density was limited, thus preventing superparasitization. The number of progeny per host egg and the ♂ proportion of the sex ratio were inversely related to the host egg density over a range of limited host densities. ZUSAMMENFASSUNG Die Biologie von Trichogramma brevicapillum Die Biologie von Trichogramma brevicapillum Pinto & Platner (gezüchtet auf Eiern von Trichoplusia ni (Hübner)) und der Einfluss einiger abiotischer und biotischer Faktoren auf die Parasitierungsstrategie der Adulttiere wurden studiert. Eier, Larven, Praepuppen und Puppen werden beschrieben. Die Entwicklung dieser Stadien bei 25° dauerte etwa 1, 3,1 und 5 Tage. Die Fortpflanzung ist bisexuell und parthenogenetisch‐arrhenotok. Die Praeovipositionsperiode dauerte etwa 3 Stunden. Die Eiablage war am grössten in der dritten und vierten Stunde der Photophase und am kleinsten in der Scotophase. Die T. ni‐ Eier eigneten sich am besten als Wirt im Blastulastadium des Embryos. Die Eignung nahm ab in den nächsten Stadien um in den späten Embryonalstadien wieder zu wachsen. Weibchen, die sich einzeln in einem Wirtset entwickelt hatten, waren wesentlich grosser und fruchtbarer als Weibchen aus Wirtseiern mit 2 und 3 Parasiten. Die Eiablage einzelner Weibchen wurde gehemmt, wenn die Dichte der Wirtseier begrenzt war; dies wirkt der Superparasitierung der Wirtseier entgegen. Die Nachkommenzahl pro Wirtsei und der männliche Anteil des Geschlechtsverhältnisses waren umgekehrt proportional zur Dichte der Wirtseier und zwar im Bereich begrenzter Dichte.

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