Tachinid parasitoids: are they to be considered as koinobionts?

Tachinids are usually considered as koinobionts as none of them kills or paralyzes the host when first entering it. These parasitoids, however, do not fit well into the koinobiont/idiobiont dichotomy because only some species show a high degree of physiological adaptation to the host, whereas the larvae of other species grow quickly following attack and kill the host rapidly, thus behaving more as idiobionts. The in vitro rearing technique provides further evidence for the poor adequacy of the koinobiont/idiobiont dichotomy for tachinids. In fact, while typical koinobionts are known to be difficult to culture on artificial media, some tachinids displaying non-synchronized development with the host have been successfully reared in vitro on insect material-free artificial media, thus behaving similarly to idiobionts. I therefore suggest not to use the koinobiont/idiobiont classification for tachinids and to class them instead only on the basis of the presence or absence of developmental synchrony with their hosts.