With the mini heat wave we experienced in early April, I rushed an email out to all current Hoverfly Lagoons volunteers to get some Lagoons out in gardens ASAP (see: The Buzz Club Hoverfly Lagoons Project webpage). The garden down here in East Sussex was teeming with hoverflies, particularly Eristalis pertinax, a honeybee mimic, and as my daughter and I were creating Lagoons out of Alexanders and grass cuttings, Eristalis hoverflies were landing and offloading eggs right in front of our eyes!
I’m hoping the project will inspire people to re-focus on the wildlife in whatever outdoor space they have available to them, and helped a little by my 5-year old, explore the lives of insects. Lagoons provide a window into a lesser-known world, and they don’t only benefit hoverflies.
APRIL – creating Lagoons for hoverflies
Lagoons can be made from any water-retaining container, but we ask volunteers to create them using plastic milk bottles because they work, they are a standard size, and they don’t cost a thing.
Creating Hoverfly Lagoons on 4th April with my 5 year old daughter (and her buddies):
MAY – first search for hoverflies in Lagoons
It has been quite extraordinary the number of hoverfly eggs that have turned up in our Lagoons so far this year. It indicates to me that this kind of habitat may be particularly limited at the moment. With a view to understanding more, new to this year we are asking volunteers to complete insect surveys in their gardens, which I hope may give us an insight into what’s happening in gardens over the Lagoon season.
This is the first year I have seen so many huge batches of eggs!
The second film I threw together is designed to give volunteers an idea of what they might find in Lagoons right now; eggs and tiny 1st-stage hoverfly larvae. At this early stage searches need to be made carefully, and if tiny larvae are found, I recommend leaving the Lagoon for a couple of weeks to allow them to grow (and/or eggs to hatch) before attempting to do a May survey.
It’s amazing what can be achieved from the comfort of ones hammock. What to look for in Lagoons in April and May:
It’s been 3 weeks since the huge batch of eggs was discovered (in the above image), so today (10th May) I searched through this particular Lagoon.
The larvae were in their 1st and 2nd stage of growth (at the end of the 3rd stage of growth, they crawl out the Lagoon and pupate in the dry leaf litter / soil). Mia joined me to search through the content, and look at it under the microscope.
Mia taking a closer look at a hoverfly larva with me, taking her dual role as student and teacher very seriously:
I created a Lagoon inside a large glass vase to enable me to view and record the decay over time, and peek inside. I thought it would be cool to see and record how deep the larvae forage.
JUNE – sometimes inspiring participation can be tricky
Late June Survey with an easily distracted 4 year old:
Excitingly, through our searches we found some ‘different looking’ pupae in our pupation trays, which we dutifully collected. They consequently emerged and turned out to be Rhingia rostrata a new species of hoverfly to add to the Lagoons list! At the larval stage, this species does not have a long breathing tube, and we know very little about its biology. What’s more, including this species in the Lagoons lineup means a different suit of flowering plants are visited and pollinated in gardens, as this hoverfly has a very long tongue. We are learning something new every year with the Hoverfly Lagoons project, and continue to demonstrate the potential of having this habitat in gardens!
July – adults have been emerging for the last few weeks, as much as I tried to get the littles involved in the first release, our priorities did not meet so alas here is the release of the first adults sin children:
August – things are cooling down now and larvae in Lagoons are already starting to ‘fatten up’ in preparation for winter. As it becomes cooler and days become shorter, regardless of body-size or stage, larvae start to become opaque with white fat (at any other time, only final/3rd-stage larvae do this as they prepare to pupate). Many larvae in Lagoons now will likely remain there over winter, waiting for spring 2021.
2-minute video illustrating the larvae in a couple of my Lagoons (plus a brief cameo from the children):
September – we’ve had a late summer, a peak in temperature in the UK this month, and it’s meant that there has been a hoverfly boom in Lagoons! It’s nearly October and I’ve counted several tiny larvae in our garden Lagoons, I wonder if they will survive.
We also have several medium to large larvae, likely reaching 3rd stage (or final stage). All these larvae are very likely to overwinter now, they will stop growing larger and start fattening up for winter, becoming visually opaque.
During winter they don’t tend to feed, though most remain in the water. It will be interesting to see how they are in a month!