[Syrphidae] RE: Raising Syrphus larvae

Mon Jun 28 16:20:43 BST 2010

Hi Graham (and Chris),

Thanks very much for your detailed reply - it sounds like the black hoverfly death is something I will have to live with, and it is has only affected a small proportion of samples. I am following the specifiations you recommend regarding damp cotton wool and using soft brushes to move them when their test tubes are fowled.

I am raising them on the grass aphid Sitobian avenae, which they seem to have no trouble with - I cant feed them fast enough! They are now onto their 8th day and look a good size. This is the first batch I have reared and wondered if you might also recommend how to allow for a successful development from larvae to pupae.

Should I leave them in the test tubes with damp wool stoppers and will they just take on their pupae shape?
Also, will I need to provide them with a substrate to attach to (other than the plastic / glass test tubes) that they can use to emerge from their casing?

Apologies for all the questions, but I also wondered how many (more!) days they may take to reach pupae stage, and then emergence as an adult? I used wild gravid females to get the eggs and hoped the turn around would be quick at this time of year, and hopefully they will not aestivate / hibernate...

Thanks again,

Matt

________________________________
From: syrphidae-bounces at lists.nottingham.ac.uk [syrphidae-bounces at lists.nottingham.ac.uk] On Behalf Of Graham Rotheray [G.Rotheray at nms.ac.uk]
Sent: 28 June 2010 10:13
To: Hoverfly discussion list
Subject: RE: [Syrphidae] RE: Raising Syrphus larvae

Dear Matt (& Chris), Re your queries about rearing aphidophagous larvae, I have reared many species over the years.  Under the rearing conditions Matt describes, you shouldn’t have any particular problems.

However, I know well the dead ‘blackened’ larvae you have encountered.  Some mortality is to be expected in cultures and there is nothing special you can do to prevent it, other than carrying on and hoping the proportion dying remains small.  The main dangers to larvae in culture are desiccation and the quality and quantity of prey.  Use of damp cotton wool plugs should ensure there is enough (& not too much) moisture in your tubes and providing small to medium sized aphids until larvae have reached the 3rd stage when they will take a wider range of prey sizes, should be OK.

Not all aphid species are suitable even for a polyphagous species like S. ribesii, and although you don’t mention what aphid species you are offering, I assume that is something you are aware of.   Also switching between aphid species presented as prey can sometimes cause mortality and should be avoided.  Larvae, especially small ones, are obviously more vulnerable and require care in handling, i.e. use a brush to move them about rather than tweezers or forceps.

After larvae have finished feeding and emptied the hind gut, they are best removed to clean tubes and gently wrapped in slightly moistened tissue paper.  Tubes should be stored in cool, dark conditions.  Depending on time of year, it will be 2-3 weeks before adults appear or larvae will aestivate for several weeks or hibernate for several months.  The tissue paper should be replaced every few weeks to prevent fungal infection.

Hope this is helpful.

All best wishes,

Graham

Graham E Rotheray
National Museums Collection Centre
242 West Granton Road,
Edinburgh EH5 1JA
Tel 0131 247 4243
________________________________
From: syrphidae-bounces at lists.nottingham.ac.uk [mailto:syrphidae-bounces at lists.nottingham.ac.uk] On Behalf Of Bergh, Chris
Sent: 27 June 2010 13:57
To: 'Hoverfly discussion list'
Subject: [Syrphidae] RE: Raising Syrphus larvae

Matt,

I have had this experience with larvae of Heringia calcarata. It has been sporadic and unpredictable, but like you, I would be interested to know if anyone has an explanation.

Cheers - Chris

Chris Bergh
Associate Professor of Entomology
540-869-2560 ext. 32

-----Original Message-----
From: syrphidae-bounces at lists.nottingham.ac.uk [mailto:syrphidae-bounces at lists.nottingham.ac.uk] On Behalf Of Perkins, Matthew
Sent: Sunday, June 27, 2010 8:28 AM
To: syrphidae at lists.nottingham.ac.uk
Subject: [Syrphidae] Raising Syrphus larvae

Good afternoon,

I could do with some advice on my hoverflies! Thanks already for those who have already offered much useful advice on my first PhD experiemnt examining food chain lengths... this email list has proved invaluable.

I have two new querries though if anyone could help:

I am raising Syrphus ribesii larvae and am keeping each larvae individually in small glass / plastic test tubes and provide them with a small leaf and lots of fresh aphids every day. I clean the tubes every day, and use damp cotton wool to plug the ends of the tube. They are kept at 70% humidity, 16:8 hours light: dark.

1. My larvae are now 6 days old and I need to know if they have any requirements for successful development into pupae - do they require something to stick too or do they need to hang upside down etc. Also should I need to keep them moist throughout their pupae stage?

2. I have recently had many (less than 25%) of different age classes turn black and die. It appears on first glance like they have not discharged their gut... but I have no idea. Does anyone recognise these symptoms or could provide advice or keeping more alive?

Thanks,

Matt Perkins

PhD Researcher
Center for Ecology & Conservation
University of Exeter,
Cornwall Campus

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