(2nd Place) Effects of phytochemicals on predatory lacewing’s development and survival

Specialist herbivore insects have developed the ability to sequester plant toxins as defense chemicals against their natural enemies. While it is assumed that specialist natural enemies have mechanisms to overcome such chemical defenses in their prey, little is known about the physiological response of generalist natural enemies to consuming chemically defended prey. To address this, we investigated the impact of phytochemicals sequestered by aphids on the development of generalist lacewings using the milkweed-aphid-lacewing system. The generalist predatory lacewing, Chrysopa oculata, preys on various small insects, including aphids. We used two aphid species, Aphis nerii, and Myzocallis asclepiadis, that exclusively feed on milkweed (Asclepidae Spp.) and sequester cardenolides from these plants. Previous research showed that C. oculata prefers A. nerii, while the higher cardenolide sequestration in M. asclepiadis. Based on this, we hypothesized that C. oculata has evolved a preference for less toxic prey due to the negative effects of cardenolides. To test this hypothesis, we reared A. nerii on different stages of common milkweed (As. syrica) and observed variations in cardenolide levels. Our results indicated that consuming A. nerii with higher cardenolide content increased mortality rates and longer developmental times in C. oculata. Surprisingly, consuming M. asclepiadis had a minor negative effect despite its higher total cardenolide concentration. It is important to note that the total cardenolide concentration alone cannot predict the negative effects on predator vital rates, as different prey species may sequester different types of cardenolides with varying toxic effects and nutritional values.