14 Jul Robberfly: Assassins of the Sky

 

 

Flies get a bad rap. Their unwanted presence on your plate of food or habit of lodging themselves at the back of your throat mid-conversation gets them swatted away or squashed without a second thought. However, flies do many essential jobs for our ecosystems. Not only are they productive pollinators and recycling warriors, some of them (like robberflies) are also master assassins!

 

Life on the Edge are collecting information about this species to aid their conservation. If you see one in our area, share your sighting with us using iRecord. Instructions on how to do this are here.

 

 

Skip Ahead:

 

 

 

 

• • Species Introduction
  • Share a Sighting
  • Performance by NDP Circus

 

 

 

 

Micheal O’Shea, Communities Trainee – Life on the Edge & Buglife

 

 

 

 

 

Species Introduction

 

 

Hunting

 

Robberflies (also called Assassin Flies) come from the Asilidae family. Their name stems from their ability to hunt by snatching other insects in mid-air, like arial assassins. Once caught, the unfortunate victim is injected with a concoction of neurotoxins and proteolytic enzymes. This mixture paralyses the victim and slowly digests their insides, which the robberfly slurps up using it’s proboscis (sharp mouth parts) like milkshake through a straw. Robberflies are not fussy – beetles, grasshoppers, crickets, bees, wasps, moths, butterflies, and even other Robberflies are on the menu!

 

 

 

Appearance

 

 

Two Robberfly species are being supported by Life on the Edge. These are the Devon Red-legged Robberfly (Neomochtherus pallipes) and the Hornet Robberfly (Asilus crabroniformis).

 

Robberflies, like all true flies, belonging to the order Diptera and have only one pair of wings. The secondary pair, which are seen on other flying insects, are replaced by a set of club-like structures called halteres. Halteres assist with balance, orientation and stability during flight, allowing Robberflies to react to disturbances in the environment and keep a stable flight posture when evading predators or conducting their own attacks.

 

Robberflies have two large compound eyes with a distinctive depression between them and long. bristly legs. Alongside the proboscis they sport a villainous moustache which provides protection against struggling victims. Helpful when your prey is stuck to your face I suppose?

 

The Hornet Robberfly is Britain’s largest robberfly and has distinct black and yellow markings on its body, resembling those of a hornet (hence it’s name). This illusion deters larger predators who would otherwise feed on robberflies but lack the palate for insects with a painful sting! This type of robberfly can grow to over an inch long and sports a thick gingery beard (mystax). The Devon Red-legged Robberfly is smaller at around 11-15mm long and is instantly recognisable thanks to it’s dazzling red/orange legs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lifecycle

 

 

The Hornet Robberfly’s lifecycle relies on insect-rich habitats and proximity to grazing animals. This is because mammals provide an unglamourous yet essential gift to the Hornet Robberfly – Poo! After mating, the female robberfly seeks out a dry pat of dung to lay her eggs. This can include cow, horse or rabbit dung. Once hatched, the larvae spend the next three years developing in their unusual nursery! These youngsters are formidable hunters, often feeding on the neighbouring larvae of dung beetles.

 

Unfortunately, this stage in the robberflies lifecycle puts them at particular threat. Ivermectin, a common de-worming drug used to control gut parasites in livestock, contaminates the faeces making it toxic to invertebrates, like robberflies. Furthermore, the loss of 97% of the UK’s wildflower meadows, largely due to agriculture and development, has decimated the number of pollinating insects. This leaves robberflies in a precarious position –  with their food source quickly diminishing.

 

The Devon Red-legged Robberfly is less well understood. These characters require south-facing, sandy slopes with plenty of warmth however they haven’t been recorded in Devon since the 1990s.

 

 

 

 

 

Share a Sighting

 

 

Directly contribute to this species conservation by sharing your sightings using iRecord and joining the Life on the Edge activity.

 

 

New to recording with iRecord? Uploading sightings is easy! Just follow these steps:

 

 

1. Download the app from the App Store or Google Play
2. Login to your account or register a new account
3. Join the Life on the Edge activity – this allows you to share your sightings with the project. Do this by clicking ‘ALL ACTIVITIES’ in the top right corner, and then selecting ‘Life on the Edge’.
4. Upload your first record! Remember, a photo helps iRecord specialists verify your finding.

 

 

If you can’t upload your sighting straight away, make a note of the location (with a digital map pin, grid reference, or What3Words), and upload later.

 

 

 

 

 

 

Performance by NDP Circus

 

 

 

The mastery of this aerial acrobat could only be portrayed by those with the skills to match, so we’ve commissioned a truly unmissable performance by the talented artists at NDP Circus who bring to you – THE LIFE CYCLE OF THE ROBBERFLY!

Featuring a live DJ, sky-high acrobatics, and a repurposed aeroplane fuselage, this performance is not to be missed!

First showing is at our “LotE Goes Wild” event at Parkfield (Paignton) on the 8th July, then outside The Box in Plymouth on Wednesday the 30th July.

See our July events page for details about where to see this remarkable theatrical performance for yourself.