# Effect of Temperature on Skipper Fly Piophila casei (Insect: Diptera) Reared on Ham

## TL;DR

This study examines how temperature affects the development of skipper flies on ham, helping to estimate infestation timelines for better food safety management.

## Contribution

The study provides new temperature-dependent development data for Piophila casei on Parma ham using ADDs and isomegalen-diagrams.

## Key findings

- The minimum development threshold for P. casei was estimated at 9.91 °C.
- ADD values for oviposition–eclosion varied between 209.2 and 220.7 depending on temperature.
- Isomegalen- and isomorphen-diagrams were used to estimate infestation times effectively.

## Abstract

Cured meats are prone to infestation by various insects, including the skipper fly Piophila casei. This small fly can damage food by tunneling into it and may act as a vector for pathogens, making the infested food unsuitable for consumption. Specifically, in ham, females lay eggs, and the newly emerged larvae feed on the product. The development time of P. casei is influenced by several factors, primarily temperature and the nature of the substrate. Determining the onset of an infestation is crucial for its effective management in terms of prevention throughout the shelf life and market life of the product. In our study, we reared P. casei on cured ham at five different temperatures and calculated the corresponding development time by means of two analytical approaches, namely accumulated degree days (ADDs) and isomegalen-/isomorphen-diagrams. These methods allow for the estimation of insect age based on accumulated thermal units, body length, or developmental stage.

The cheese (or ham) skipper, Piophila casei (Linnaeus), belongs to the family Piophilidae and is a detritivore species that feeds on decaying organic matter. Its larvae are commonly found on high-protein substrates (including carcasses), with a life cycle that is strongly influenced by environmental temperature and food nature. In this study, we investigated development time and larval length of P. casei reared on Parma ham PDO (Protected Designation of Origin) at five constant temperatures (20, 22, 24, 26, 28 °C). We calculated the accumulated degree days (ADD) and constructed isomegalen- and isomorphen-diagrams to estimate the infestation time. The minimum development threshold (tL) obtained by extrapolating the development rates measured between 20 °C and 28 °C was 9.91 °C, resulting in ADDs (oviposition–eclosion) of 216.9, 219.9, 220.7, 209.2, and 220.1 at 20, 22, 24, 26, and 28 °C, respectively.