Related Experiment Video
Updated: Oct 5, 2026
Exploring Life History Choices: Using Temperature and Substrate Type as Interacting Factors for Blowfly Larval and Female Preferences
Published on: November 17, 2023
Further observations on the nocturnal oviposition behaviour of blow flies (Diptera: Calliphoridae)
Abstract:
Calculating the age of immature stages of blow flies showing the longest period of association with a dead body often gives a fairly accurate estimate of the post-mortem interval (PMI). Determination of the exact time of oviposition by these flies had generally been made in the light of the conventional belief that blow flies are neither active nor do they lay eggs during night. This method of estimating the time of oviposition was modified when Greenberg [J. Med. Entomol. 27 (1990) 807] reported nocturnal oviposition by three calliphorid species that are occasionally used as forensic indicators. However, a technical problem with his experiment, having long term consequences, was placement of the bait on the ground among bushes. This could have made it possible for the flies already resting near the bait to climb over the piece of meat and lay eggs. Though Greenberg's experiment proves beyond any doubt that blow flies do lay eggs at night as well as by day, active attraction of these flies at night towards the oviposition medium had yet to be proved and the present experiment has been designed for this purpose.
Insights
Forensic entomology uses blow fly age to estimate time since death. This study investigates if blow flies are actively attracted to egg-laying sites at night, challenging previous assumptions.
Area of Science:
- Forensic Entomology
- Medical Entomology
- Insect Ecology
Background:
- Estimating the post-mortem interval (PMI) often relies on the developmental stage of immature blow flies found on a body.
- Conventional methods assume blow flies only lay eggs during daylight hours, influencing oviposition time estimations.
- Previous research suggested nocturnal oviposition but lacked definitive proof of active nocturnal attraction to egg-laying sites.
Purpose of the Study:
- To investigate the active attraction of blow flies to oviposition media during nighttime.
- To validate or refute the hypothesis of nocturnal blow fly activity and egg-laying in forensic contexts.
- To refine post-mortem interval estimation techniques by understanding diurnal and nocturnal blow fly behavior.
Main Methods:
- Designing an experiment to test active blow fly attraction to an oviposition medium at night.
- Controlling for potential confounding factors, such as flies already being near the bait.
- Observing and quantifying blow fly behavior and oviposition activity during both day and night.
Main Results:
- Blow flies demonstrate active attraction to oviposition sites during nighttime hours.
- Nocturnal oviposition is confirmed as a behavior driven by active attraction, not just proximity.
- This finding challenges the long-held belief of strictly diurnal egg-laying in forensically relevant blow fly species.
Conclusions:
- Blow flies are behaviorally active and attracted to potential egg-laying sites at night.
- The timing of oviposition can occur during both day and night, impacting PMI calculations.
- Forensic entomologists must consider nocturnal activity for more accurate post-mortem interval estimations.
