Photoperiodic Regulation of the Daily Rhythm of Trichogramma Adult Emergence (Hymenoptera, Trichogrammatidae)

Abstract

Laboratory experiments demonstrate that the adult emergence rhythms of two Trichogramma species (T. telengai Sor. and T. principium Sug. et Sor.) significantly depend on photoperiod. The synchronicity of adult emergence is maximal at day lengths of 12–16 h. Under longer days (18–20 h) adult emergence is extended, whereas under very short days (4–8 h) a substantial proportion of adults emerge before light-on. The pattern of T. telengai emergence under day length of 4 h suggests the possibility of the existence of two fractions (the first that emerges in the dark and the second that waits for light-on) which results in two peaks of emergence. As a whole, these data agree well with the hypothesis of the periods of “potential readiness” and “obligate activity” forwarded by V.B. Chernyshev. The results of the study can be used for optimization of the methods for laboratory and mass rearing of Trichogramma species.