Host age selection

Host age selection by Tachinidae:

Earlier, Reed  (1965) reported that V and VI Instars larvae of H. armigera attacked with 25 per cent parasitism by Drino imberbis (Wiedemann). Goniophthalmus halli (Mesnil) parasitised the VI instars larvae of H. armigera and one individual emerged from each host   pupae. Chauthani and Hamm (1967) recorded that 10 to 14-day-old larvae of Heliothis zea (Boddie) and Spodoptera frugiperda (Smith) were parasitised by Drino munda (Wiedemann). Achan et al. (1968) studied four tachinid parasitoids of H. armigera and reported that Palexorista imberbis preferred medium sized larvae; Senometopia =Carcelia illota laid eggs on inactive full-grown larvae or on prepupae, Exorista fallax (Meigen) preferred very active late instars larvae and Goniophthalmus halli laid eggs on full-grown host larvae or prepupae.

The host age selection by S.illota on H.armigera is studied by Chaudhari, (1996). S.illota preferred VI instars (18-19 days old) larvae for parasitism. No parasitoid emerged from I and II instars larvae, as the female do not oviposit on them. The number of parasitoids emerged were 18, 37, 44, and 53 from III, IV, V and VI instars host larvae, respectively. Maximum (42.4 %) parasitism was recorded with VI instars (18-19days old) larvae (Chaudhari, 2003).  From parasitised III and IV instars larvae the maggots emerged were small and puparia formed were comparatively smaller than those on V and VI instars larvae. When the eggs were deposited on III and IV instars larvae, the parasitoid maggot emerged from VI instars larvae or by killing the prepupa. From egg deposited on V and VI instars host larvae, however, parasitoid maggot emerged from host pupae by killing it after complete feeding. The puparia formed were larger and adults emerged were healthy. The parasitoid females preferred to oviposit on newly moulted host larvae. The statistical analysis revealed that a positive and highly significant correlation existed between host age and percent parasitism (r = 0.9775).