Effect of cold storage on the pupal development of two pollinators, Eristalinus aeneus and Eristalis tenax

Abstract

Eristalinus aeneus (Scopoli) and Eristalis tenax (L.) (Diptera: Syrphidae, Eristalini) are important pollinator species that can be artificially reared and commercialised. To achieve better control over the pupal development time and adult emergence, cold storage techniques are suitable tools. Insects were reared under controlled conditions: 25 AE 1 °C, 50% r.h., and L12:D12 photoperiod. Pupae of both species were stored at 5 °C at the beginning (early treatments) or at the end (late treatments) of their development for various periods of time (5, 10, 15, 20, or 30 days). Development stopped completely at 5 °C in both treatments, but in general, pupae stored at the beginning of the pupal stage provided better results in terms of survival (adult emergence) and quality of the adults (general morphology). The cold tolerance of E. tenax was lower than that of E. aeneus, with their pupal developmental time successfully extended up to 18 and 23 days, respectively, without compromising survival and morphology. The number and types of morphological alterations due to cold storage were recorded.

Sexual size and shape dimorphism, and allometric scaling in the pupal and adult traits of Eristalis tenax

“…We observed that PDT highly overlapped between sexes and populations, and as such, the lack of sex differences in PDT is consistent with the published findings on the pupal development of drone fly (Campoy et al, 2022; Campoy, Sáez, et al, 2020). It is important to highlight that difference among sexes, populations, and/or species in body size and shape might reflect differentiation in the rate and duration of cell growth and division underlying the changes in hormonal pathways (Shingleton et al, 2007).…”

“…Given that complex metabolic change at the final larval instar (Truman, 2019; Truman & Riddiford, 2019; Zhang et al, 2019) is associated with body's terminal growth period and the beginning of pupation, adult size in holometabolous insects is limited by the size of the larvae (Shingleton et al, 2007). Hence, a lack of SD in PDT in drone fly (herewith and Campoy et al, 2022) suggests that SSD obtained in both pupal and adult traits reflects developmental changes which occur during the larval stage. For instance, longer larval developmental time (LDT) in the males of E. arbustorum was suggested to be linked with male‐biased SSD observed in the length of second tergites in adults (Ottenheim et al, 1995).…”

Optimal cold storage protocol for Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), a biological control agent for coleopteran pests in stored products

“…Similar findings have been observed in other species, including Eristalinus aeneus (Scopoli) (Diptera: Syrphidae) and Eristalis tenax (L.) (Diptera: Syrphidae), where the emergence rate of early pupae stored at 5 °C surpassed that of late pupae 27 . Conversely, investigations on endoparasitoids such as Microplitis manilae (Ashmead) (Hymenoptera: Braconidae) and Psyttalia incise (Silvestri) (Hymenoptera: Braconidae) suggest that mid‐stage pupae are more suitable than early‐ or late‐stage pupae for cold storage 28,29 . Thus, determining the proper age of parasitoids is critical for ensuring successful cold storage, and temperature is a key abiotic factor that determines parasitoid survival in cold storage.…”

“…27 Conversely, investigations on endoparasitoids such as Microplitis manilae (Ashmead) (Hymenoptera: Braconidae) and Psyttalia incise (Silvestri) (Hymenoptera: Braconidae) suggest that mid-stage pupae are more suitable than early-or late-stage pupae for cold storage. 28,29 Thus, determining the proper age of parasitoids is critical for ensuring successful cold storage, and temperature is a key abiotic factor that determines parasitoid survival in cold storage.…”