# Development and Competition of Three Parasitoid Wasps, Brachymeria podagrica, Dirhinus himalayanus, and Nasonia vitripennis, in Their Host, Sarcophaga dux, in Single and Mixed Infections

## TL;DR

This study compares how three parasitoid wasps develop in a flesh fly host, both alone and together, with implications for forensic investigations.

## Contribution

The study provides new empirical data on competitive interactions among parasitoid wasps in a shared host under controlled conditions.

## Key findings

- Nasonia vitripennis outcompeted Brachymeria podagrica and Dirhinus himalayanus in mixed infections.
- Dirhinus himalayanus failed to develop when co-infected with Nasonia vitripennis.
- Uninfected Sarcophaga dux pupae had a high emergence rate of adult flies.

## Abstract

Laboratory trials were carried out to investigate the development of three entomophagous parasitoid wasps in preimaginal stages of Sarcophaga dux in monoinfections and mixed infections. Laboratory-raised postfeeding S. dux third-stage larvae were exposed to Brachymeria podagrica. After pupation, 50 of these fly puparia were brought in contact with pupal parasitoid Dirhinus himalayanus and 50 with Nasonia vitripennis, and the remaining 50 puparia were left as Brachymeria monoinfection. In three further trials, each set of 50 freshly pupated host puparia from the same source was exposed to N. vitripennis and D. himalayanus, as monoinfections and mixed infections, respectively. The uninfected control group consisted of 50 S. dux larvae that were kept separately under the same conditions. The percentages of successfully developed B. podagrica and D. himalayanus in monoinfections were 56 and 86%, respectively, and progeny of N. vitripennis hatched from 88% of the exposed host puparia. In mixed infections, N. vitripennis dominated over B. podagrica and D. himalayanus with rates of successfully infected hosts of 50 and 94%, respectively. The number of Nasonia progeny in these groups ranged from 4 to 49 and 5 to 43, respectively. Dirhinus himalayanus did not develop in the simultaneous infection with N. vitripennis. Not a single S. dux eclosed in the six experimental groups, while in the uninfected control group, 46 (92%) adult flies eclosed 11 to 14 days after the start of pupation. Since the three parasitoids emerge from flesh fly pupae, these insects can become important in criminal forensic investigations when corpses are in an advanced stage of decay. More data on their preimaginal development at different temperatures are necessary.