Rhingia rostrata

Female R. rostrata

While this could be a one-off i.e. the work of a single confused female, I was delighted to discover three Rhingia rostrata pupae in one of my grass-filled Lagoon’s pupation tray! It was discovered among many Myathropa florea pupae, and due to it’s small size and shape, could easily be overlooked (see images below).

A Rhingia rostrata pupa (left) and Myathropa florea pupa (right)

As you can see, R. rostrata‘s much smaller pupa, lacking a breathing tube, could very easily be missed when searching pupation trays, so DO try and look out for these! These were collected on 23rd June.

Key features of R. rostrata pupa include the anterior spiracles, little delicate projections from the head end from which they breath, and the posterior respiratory processes, which is an often shiny projection at the back end
Freshly emerged R. rostrata male

This species turned up in (was attracted to) a very dense Lagoon I created on 4th April as an experiment to determine how fast densely packed Lagoons take to rot down to liquid, and if a different suit of hoverfly species might be attracted to dense versus more liquid Lagoons.

The dense grass-filled Lagoon which R. rostrata developed in, they likely remained in the top inch, you can see the darkened rotten top layer here
This Lagoon was packed full of Myathropa florea larvae (seen here), and muscid larvae, but I couldn’t find any Rhingia larvae, after finding the pupae (thoroughly searched 28th June)

This species’ larval and pupal stages have not yet been described, we know very little about where the larval stage develops. So this is a particularly exciting discovery.

All 3 emerged within days of each other, two males (27th and 29th June) followed by one female (1st July). I fed them honey / water solution, and offered them flowers.

Feeding from the honey solution on kitchen paper, demonstrating their long tongues quite nicely
Female (left) and male (right) R. rostrata

One R. rostrata female was recorded feeding on red campion in the same garden on 19th May, perhaps this was the one that oviposited a few eggs in this Lagoon which was metres away, see her below.

Whether it was the flowers or the Lagoon that attracted this species, either way both were visited and both are likely important, so get gardening for hoverflies!