Campoletis sonorensis

Pacheco, Henry Murillo, Vanlaerhoven, Sherah & Garcia, M. Angeles Marcos, 2021, Host suitability of Trichoplusia ni and Chrysodeixis chalcites (Lepidoptera: Noctuidae) for native and nonnative parasitoids expanding their host range, The Canadian Entomologist 153 (2), pp. 137-149 : 140-141

Campoletis sonorensis

Parasitoid success of C. sonorensis was similar on T. ni and C. chalcites (F 1,18 = 1.28, P = 0.273; Fig. 1 ). Host success and host mortality were higher amongst parasitised T. ni than amongst C. chalcites , but parasitoid cocoon mortality was lower (F 1,18 = 8.05, P = 0.011; F 1,11.38 = 25.07, P <0.001; F 1,10.61 = 12.68; P = 0.005, respectively; Fig. 1 ). Host mortality was higher amongst parasitised T. ni than amongst nonparasitised T. ni (F 1,18 = 7.31, P = 0.015; Means ± SE: 4.00 ± 0.73 and 1.80 ± 0.36 dead larvae, respectively), but for C. chalcites , host mortality amongst parasitised larvae was similar to that amongst nonparasitised larvae (F 1,18 = 1.16, P = 0.296; Means ± SE:

1.60 ± 0.43 and 2.20 ± 0.36 dead larvae, respectively). The host success of parasitised hosts was mostly associated with the cuticular encystment of parasitoid eggs ( Vinson and Iwantsch 1980b; Namba et al. 2004). On more than 50% of the surviving parasitised hosts, host larvae were observed moving the parasitoid eggs from the insertion locations in their bodies to the ends of their bodies, then isolating the eggs in bubble-like extensions that developed on top of the hosts’ last abdominal segments.

Multinomial logistic regression indicated a difference in the interaction of host success (Wald = 17.545; df = 1; P = 0.001), host mortality (Wald = 10.995; df = 1; P = 0.001), and parasitoid cocoon mortality (Wald = 14.798; df = 1; P = 0.001) with parasitoid success between parasitised T. ni and C. chalcites by C. sonorensis . The success of C. sonorensis declined more on T. ni than on C. chalcites with the increase of host success (Coefficient = 2.577) and host mortality (Coefficient = 1.066); however, it declined less than on C. chalcites with the increase of parasitoid cocoon mortality (Coefficient = − 1.555).

The development times from oviposition to cocoon formation, cocoon to adult emergence, and oviposition to adult emergence of C. sonorensis reared on T. ni were shorter than on C. chalcites (U = 1562.50, P <0.001; U = 6567.00, P = 0.010; U = 1900.50, P <0.001, respectively; Fig. 2 ). The mean sex ratio was slightly female-biased on T. ni (0.48 ± 0.08) and male-biased on C. chalcites (0.66 ± 0.08), but not significantly different between them (F 1,18 = 2.65, P = 0.121).

Figures

Fig. 1. Suitability parameters of hosts Trichoplusia ni and Chrysodeixis chalcites parasitised by Campoletis sonorensis. Parasitoid success is expressed as the number of hosts from which adult solitary or gregarious parasitoids are developed. Parasitoid cocoon mortality is expressed as the number of developed cocoons from which adult parasitoids did not emerge. The host success is measured as the number of hosts that developed into adult moths, whether the host was parasitised or not. Host mortality is calculated from the number of hosts that died after parasitism without developing into a moth or parasitoid. Sample size = 20; replicates = 10. Note: Means (±SE) with the same letter are not significantly different (P> 0.05). Parasitoid success and host mortality were analysed using analysis of variance (ANOVA), and parasitoid cocoon mortality and host success were analysed using Welch’s ANOVA.

Fig. 2. Development times in days for Campoletis sonorensis and Cotesia vanessae on Trichoplusia ni and Chrysodeixis chalcites. White: days from oviposition to cocoon formation; light grey: days from cocoon to adult emergence; dark grey: days from oviposition to adult emergence. Means (±SE) with the same letter within each parasitoid species are not significantly different (P> 0.05). Parameters were analysed using Mann–Whitney U tests for independent samples for each parasitoid species and each parasitoid development stage separately.