There are 261 British species of Tachinidae, otherwise known as "Bristle Flies", "Parasite Fies" or "Parasitoid Flies". All species have larvae which are parasitoids of other invertebrates, often butterfly or moth caterpillars (a parasitoid means a parasite that eventually kills its host). Here are the species we have photos of from Peartree Green
Bithia spreta
Flies whose larvae are known to be parasitoids of the Sulphur Knapweed Moth on the Continent but their host preference in the UK is unknown
Photos: Geoff Frampton (seen on our August Bug Walk 2024)
Cistogaster globosa - Bishop's-mitre Parasite Fly
Small flies whose larvae are parasitoids of the Bishop's-mitre Shieldbug (Aelia acuminata) (for a photo see our Bugs page). Males of this fly are quite colourful but females are mostly black
Photos: Geoff Frampton (seen on our July 2025 Insect Survey Walk)
Ectophasia crassipenis
Flies whose larvae are parasitoids of shield bugs and other hemipteran bugs. This species was first seen in Britain in 2019 and has become quite common near the south coast, though is rarely seen elsewhere
Photos: Geoff Frampton (seen on our Wildlife Walks in 2024 and 2025)
Eriothrix rufomaculata
A common species often seen visiting flowers. Their larvae are parasitoids of moth caterpillars
Photos: Geoff Frampton (seen on our Insect Walks in 2023 and 2024)
Frontina laeta
A large fly whose larvae are parasitoids of hawkmoth caterpillars. When first spotted at Peartree Green in July 2023 this was a nationally scarce species with fewer than 30 UK records, but sightings have increased in 2025
Photos: Geoff Frampton (seen on our July 2025 Insect Survey Walk)
Gymnosoma rotundatum - Ladybird Fly
Very distinctive flies with a spotted round abdomen whose larvae are parasitoids of shieldbugs
Photos: Geoff Frampton (seen on our August Bug Walk 2024)
Meigenia species
There are three British Meigenia species, whose larvae are all parasitoids of leaf beetles (Chrysomelidae)
Photos: Geoff Frampton (seen on our June 2024 Insect Walk)
Nemoraea pellucida
A very scarce species with only around 10 UK sightings. Their larvae are known to be parasitoids of moth caterpillars in southern Europe but their host preference in the UK is unknown
Photo: Geoff Frampton (August 2024)
Phania funesta
Common flies that often visit flowers but are likely to be overlooked as they are rather small. Their larvae are parasitoids of shieldbugs
Photos: Geoff Frampton
Phasia obesa
Large flies whose larvae are parasitoids of heteropteran bugs
Photos: Geoff Frampton
Siphona species
There are 19 British species of Siphona which are difficult to separate in photos. Their larvae are parasitoids of a range of other insects which vary according to the Siphona species
Photo: Geoff Frampton (seen on our August Bug Walk 2024)
Voria ruralis
Flies whose larvae are parasitoids of a range of moth caterpillars, especially those in the Noctuidae family
Photo: Geoff Frampton (seen on our August Bug Walk 2024)