Rearing Homopteran-Predatory Syrphid Larvae

My experience with rearing Syrphids is limited to aphid-eating predators. For information about rearing larvae that don't feed on aphids, refer to Rotheray, 1993 (see footnote*).

With the assistance of @edanko, I have reared three Syrphine species: Allograpta obliqua, Eupeodes americanus, and Syrphus knabi. All three of the genera predate on aphids. Here's how I went about it:

First, put the larva in a small, preferably plastic, container. You can choose to put a layer of paper towel on the bottom right now if you wish. Put a layer of paper towel covering the opening of the container, and attach with a rubber band.

Next, you'll want to find a healthy colony of aphids to harvest from. If possible, it's preferable to take from the colony you found the larva on. Every morning and every evening, depending on how fast your larva eats, take a leaf of aphids and put it in the container with the larva. This worked for me, but I'm sure there are more efficient ways of doing that.

Once the larva pupates, if you didn't already, put paper towel on the bottom of the container so it doesn't roll around. Now, all you have to do is wait. Check on the pupa throughout the days to see if the fly has emerged. Once it has, your time to photograph it is limited.

My method to photograph is to put the container in a large ziploc bag, and push the lens through the opening of the bag, leaving as little space as possible for the fly to escape. Hopefully, at this point it's recently eclosed, so it won't fly that much.

Once you have the necessary photos, you can try, if you're confident enough, to get the fly on your finger or another rigid object, and carry it outside. There, you can get better photos with nice lighting, and once the fly is ready, it can leave your finger and fly away.

Thanks for reading! I hope this is helpful. If you have any ideas or suggestions, please leave them in a comment or message me so I can edit this post. This is somewhat of a wiki, as I want this to be a good resource for rearing predatory Syrphids. See comments below from other people with experience in this for some more tips.

*(See p. 26:

Publicado el agosto 9, 2021 03:29 TARDE por zdanko zdanko


@trinaroberts Any additions or edits?

Publicado por zdanko hace casi 3 años

Similar methods here, successful so far with Allograpta obliqua (multiple), Eupeodes fumipennis, Scaeva affinis, and Leucopis (non-syrphid but similar) . I use glass pint jars covered with a piece of nylon stocking. I carefully remove each leaf onto a sheet of white paper when I want to take photographs. All larvae but one have pupated on a stem or dry leaf, and I've left them in the jar until they were nearly ready to emerge, then transferred them leaf and all to a flat clear plastic box where they can emerge and that I can photograph through, or open carefully if I'm sure they can't fly yet.

Other notes:

Leaves that hold their moisture well and have lots of aphids might not need to be changed or added very often.

Even in very dry conditions (outside ambient RH down to ~6% at least once during this) it does not seem to be necessary to worry about humidification as long as you are adding in fresh leaves and aphids.
If you add whole leaves with fresh aphids, be aware that you might also be adding more syrphids as eggs or tiny larvae, caterpillars, parasitoids...
If you start with a small larva, take some photos when it changes size and shape or molts into a new instar! We could use some good data about how they develop.
Be careful before opening your enclosure, as your larva or other creatures might be hanging out on the covering or around the opening waiting for a chance to make a break for it.

Publicado por trinaroberts hace casi 3 años

I'm not seeing anything about time frame. For we newbies, how long a process from beginning to end? Thanks :)

Publicado por robinellison hace casi 3 años

Good point! I haven't had a chance to rear a larva from first instar to adult, but either way, it seems to vary by species, or individual. @trinaroberts will probably have a better idea about the time frame.

Publicado por zdanko hace casi 3 años

@robinellison I don't know exactly how long from hatching (I've never managed to follow one all the way along). But most people don't find those anyway as they are barely big enough to see. Allograpta seem to spend about a week in what must be the 2nd instar, then 7-8 days as the final instar, then 10-11 days in the pupa. My one Eupeodes was relatively grown up when I found it, took 8 more days to pupate, and emerged 15 days after that. So, definitely some variation, but I'd say if you find a biggish larva there's a good chance the rest of the process will take 2-4 weeks. @zdanko is that consistent with your observations?

All of these are species with multiple generations per year, and not in late fall. If you find one that wants to overwinter as a larva or pupa, and emerge in the spring, that would change the timeline dramatically.

Publicado por trinaroberts hace casi 3 años

Yeah, the larvae (and one pupa) I had all took a couple of weeks. The pupa obviously took less time. One of the larva was close to pupating, so it took slightly less time than the last larva.

Publicado por zdanko hace casi 3 años

Okay, thanks very much @zdanko @trinaroberts . This was so tiny I'm surprised I saw it. Will be on the lookout for others now. Thanks again!

Publicado por robinellison hace casi 3 años

Awesome! You're in the range for A. exotica, so that would be great if you can get your hands on another larva!

Publicado por zdanko hace casi 3 años

Wow, great! :)

Publicado por robinellison hace casi 3 años

Nice read! With the exception of one Episyrphus balteatus I did not attempt to raise syrphids yet, but rather focused on leaf miners.
The success rate of getting adult flies out is rather low, mostly I end with having tiny hymenopterans in the jar... 🤨
So, I am interested to hear how often you end with parasitoids hatching.

Publicado por carnifex hace casi 3 años

None of my flies have had parasitoids, it seems (from reading around) that it's not likely with Syrphids.

Publicado por zdanko hace casi 3 años

I've had parasitoids 1 out of 4 attempted rearings.

Also worth noting:
-if you find a pupa attached to a stem or leaf, you can usually remove the pupa safely to watch what emerges
-if you find a last-instar larva (large and plump compared to earlier instars) you may be able to rear it to adulthood without offering additional food, if you cannot make any available.

Publicado por edanko hace casi 3 años

Note: we've taken to using a paper towel held onto the lid of a container instead of a screen. The paper towel still lets air through , but aphids and small things can't escape and it's easier to find than screen. Maybe update text?

Publicado por edanko hace más de 2 años

sometimes we take photos thru a plastic bag like this, and if it's a fresh clean plastic bag it works pretty well:

Publicado por edanko hace más de 2 años

Edited text.

Publicado por zdanko hace más de 2 años

The Eupeodes pomus/americanus I've successfully reared so far seem to all spend right around 7 days as a pupa. One that I raised to an adult I'd gotten really lucky with and found the egg that I was fairly certain was laid on the plant right before I found it. This one took 7 days from egg to larva to pupation, and then another 7 days as a pupa before the adult emerged. Ones that were parasitized had the wasp emerge about 14 days after pupation.

I wonder if the development speed is dependent on temperature and light like it is with some lepidoptera. I kept the rearing containers in my garage because I didn't want the aphids flying out in the house when I opened the containers to check on them. The garage has just a few small windows and isn't insulated or conditioned at all.

I've also wondered about humidity needs in the pupal stage. As larva they get moisture from the aphids and plant material. When they pupated I removed the excess plant material and debris from the container and left a small piece of paper towel by the pupa. On some of the earlier ones I raised I would put a drop or two of water on the paper towel by the pupa when I checked on them to kind of mimic morning dew, but then figured it probably wasn't necessary and stopped doing it.

Publicado por molanic hace más de 2 años

Something I found that works well for containers is small clear plastic food containers with lids. I use a utility knife to cut out the center of the lid, just leaving an outer ring . Most thin fabrics will fit under the ring to hold it down nice and taut and not have to mess with rubber bands. I have a ton of small scrap pieces of floating row cover fabric to use which is very breathable and lets light in, but is designed to keep out (or in) even the smallest insects.

You can write notes on the containers with a china marker and it comes off easily with a white vinyl pencil eraser. Sharpie also wipes well off most surfaces with a little rubbing alcohol. I wrote the container numbers on the containers and then take a photo of the number before I photograph the insect to keep them straight while processing the photos on my computer.

Publicado por molanic hace más de 2 años

not have to mess with rubber bands

That's a great idea! Only issue for me is that I like to use old pill containers, so this doesn't work as well.

Publicado por zdanko hace más de 2 años

I had another wasp emerge today. They all seem to be Diplazon laetatorius. I'm curious about this info on them from BugGuide:

This species likely has the greatest geographic range of any ichneumonid (and perhaps any hymenopteran) having been recorded from the Canadian Arctic to Argentina, from Norway to South Africa and Japan to New Zealand including many remote oceanic Islands. As with the subfamily, the vast majority of host records of D. laetatorius are from Syrphidae (20 genera). Its wide range is likely a result of human agriculture that has spread it along with aphids and aphidophagous syrphids. Because it parasitizes aphidophagous syrphids it can be considered a pest.
It has been reported to parasitize as many as 75% of syrphid larvae.

That seemed like a pretty high percentage to me. But, so far I have 9 successful syrphids raised, 5 parasitized by these wasps, 5+ that died at some point of something else, and 14 still "in progress"... but likely also parasitized I think.

Publicado por molanic hace más de 2 años

Perhaps 75% refers to species number so that 75% of syrphid larva species are parasitized but not necessarily 75% of individuals.

Publicado por bugologist2 hace más de 1 año

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