Identifying Blow Flies - Part 2

Olga Sivell currently studies at the Jill Dando Institute of Security and Crime Science, University College London carrying out research in Forensic Entomology. Her current project is on spatial and temporal distribution of Calliphoridae in Britain. She works at the Natural History Museum, London as a Research Assistant on the Darwin Tree of Life Project.

A New Identification Guide to British Blow flies: The Structure and Approach of the Blow flies Guide

I have just published a new guide to blow flies, in the Royal Entomological Society Handbooks series. It’s presented in an innovative and original way, using high quality colour photographs throughout. This new and up-to-date guide will appeal to both enthusiast and professional entomologists. There have been significant taxonomic changes among the blow flies in the last decade, so existing identification guides are now out of date. The most recent treatment of British species (Blow flies Naturalists’ Handbook by Zakaria Erzinçlioğlu, 1996) largely follows the considerably outdated Kloet & Hincks (1976) checklist. Blow flies of Fennoscandia and Denmark by Knut Rognes (1991) is more up to date, but its geographic coverage is different. The new RES Handbook has been developed as part of my PhD research.

How do the Keys Work?

The identification key is divided into several sections :

(a) Calyptrate vs Acalyptrate Flies: Showing how to distinguish between these two major groups of flies.

(b) Key to Families: Distinguishing Calliphoridae, Rhiniidae and Polleniidae from other families of calyptrate flies.

(c) Key to Subfamilies: Allows identification to subfamily level and in some cases to species (when a subfamily is represented only by one species).

(d) Key to Genera and Species: Arranged by subfamilies, this part of the key allows identification to species level.

This identification guide relies heavily on visual aids. Most characters are shown in photographs and/or drawings in order to make the task of identification easier. Each couplet is divided into two parts, one on the left, the other on the right. A character or group of characters are presented on both sides of the couplet allowing a like-for-like comparison. Further guidance is given in the Species Accounts.

What Specimen Preperation is Required?

Specimen preparation can be a significant barrier for non-specialists. Not everyone has access to expensive equipment and laboratory facilities. Fortunately, adult blow flies are one of the more accessible groups for enthusiasts to identify. It is often possible to recognise the genus by observing the general morphology.

In fact many species can easily be taken to species level using external characters. In the genus Calliphora (bluebottles), all 6 species are straightforward to identify without genital examination. Moreover, in the Melanomyinae, comprising 6 species in 4 genera, all species are easily distinguished using characters given in the key. Although the majority of British blow flies do not require microscopic examination for species-level identification, in a few instances it is helpful or even essential. So, as well as including diagnostic characters in the keys, I have also written a genitalia-based key for males in the more difficult genera Bellardia, Calliphora, Cynomya and Lucilia.

Dealing with Blow Fly Look aikes

Most blow flies have a metallic appearance, which helps to distinguish them from other flies. However, because there are other metallic calyptrate flies, especially tachinids and muscids, I have included a guide to common look-alikes. There are a few non-metallic blow flies covered in this section as well. My experience is that confusion can arise at different points, so I have dealt with lookalikes in three sections of the book.

(a) Calyptrate vs Acalyptrate Flies: One page of annotated photos distinguishing these two groups.

(b) A simplified Key to the Calyprate Families: the diagnostic characters for Calliphoridae, Rhiniidae, Polleniidae, Tachinidae, Sarcophagidae and a few others.

(c) An Additional Photo Comparison Section of the Major Confusable Look-alikes: This section highlights additional distinguishing characters. It will be especially useful for verifying records where there are only photographs and no specimen.

Any records made of blow flies can be submitted to iRecord and if you're interested in learning more about recording these fascinating insects, you can get in touch with the Blow fly recording scheme through their website.

The guide is available to order from the FSC website: https://www.field-studies-council.org/shop/publications/blow-flies