S. Ya. Reznik and N. P. Vaghina. 2007. Effect of Experience on Response of Trichogramma buesi Voeg. and T. principium Sug. et Sor. (Hymenoptera, Trichogrammatidae) Females to Different Ages of Host Eggs. 
Entomological Review, 2007, Vol. 87, No. 1, pp. 1–10. 

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Laboratory experiments have demonstrated that patterns of distribution of T. principium and T. buesi females by the number of mature ovarial eggs is strongly dependent on the age of the host (Sitotroga cerealella) eggs offered for parasitization. The approximate percentage of parasitizing females estimated from these distributions was 1.5–2 times higher for females offered young host eggs than for those offered “old” eggs, that had developed for six days at a temperature of 20°C. In both species, females more often oviposited in old (non-preferred) eggs when they had previously experienced fresh (preferred) eggs. This result contradicts the widely accepted assumption that in insect parasitoids, experience of parasitizing a preferred host decreases the probability of parasitizing a non-preferred host. One might expect that under natural conditions, a rather long time interval also precedes parasitization of less preferred host eggs by  Trichogramma females, and duration of this interval may be also dependent on availability of other host species.