Advice pls re endless Greater Water Boatmen

[Dillybythesea]

I am alarmed by the dozens of baby backswimmers we seem to have in our new (as of last autumn) nature pond. I can't but think that if they all grow up it'll be curtains for anything living. Do they have a predator that will swing into action, please? When I took a (fuzzy, sorry) picture of one today, it seemed to be carrying something? I can't think it was doing its lifeguard training so is this what they do with prey? Any info gratefully received!

[Gill Catton]

Yes these are predatory but perfectly natural even though they can build up into large numbers this is ok. This is one of the reasons frogs and other aquatic animals have quite so many babies and some always get through. Put in some plants like hornwort if you get a bit worried so the other animals can hide. (backswimmers seem to prefer to catch things in open water)

Backswimmers can also fly so that's how they first turned up. And they feed by inserting a needle-like mouth part into prey (so prey will remain whole most of the time).

[Dillybythesea]

Thanks Gill - that sounds a bit reassuring. I can certainly add some more cover. ATB!

[Tobyh]

I was quite pleased when I saw these in my pond - just over the weekend there appears to have been some sort of hatch. My pond is only a year old this month so still learning here.

Personally I would think, as Gill says, there are so many other predators that will pick them off, only a few will survive. I know i have loads of dragonfly larva, damselfly larva, beetles and newts that i'm sure will tuck into them.

I see your pond is fairly new too but I'm sure it will balance out in the end.

TobyH

[Mark Burgess]

Notonecta are cannibalistic; adults and larger nymphs preying on the smaller instars. You’ll probably end up with a couple of really big ones in a few weeks.

(I can’t find the ref., but it’s one of Macan’s)

[Dillybythesea]

Many thanks to all. I have to say that in the absence of any obvious signs of dragonfly and damselfly larvae, or beetles or newts, like Toby, it's great to hear these are cannibalistic and should sort themselves out over time. And talking of cannibalistic makes me think I'll post yesterday's conundrum - which was a pair of - are they called hog lice? asellus aquaticus - locked in an embrace, but deadly or passionate I'm not sure! ATB, Dill

[Gill Catton]

Originally Posted by Dillybythesea

Many thanks to all. I have to say that in the absence of any obvious signs of dragonfly and damselfly larvae, or beetles or newts, like Toby, it's great to hear these are cannibalistic and should sort themselves out over time. And talking of cannibalistic makes me think I'll post yesterday's conundrum - which was a pair of - are they called hog lice? asellus aquaticus - locked in an embrace, but deadly or passionate I'm not sure! ATB, Dill

If they are indeed hog lice (sounds right to me) That'd be passionate

[Malcolm Banks]

Hog lice are fascinating but if I could just jump back to the backswimmers, I still have about half a dozen adults that have overwintered. Two months ago they appeared to be on their last legs, festooned with fungus (saprophytic I was told), but they have acquired a new lease of life. I guess the increase in temperature and the commensurate increase in activity have allowed them to shake off the fungus, which had probably accumulated as a result of long periods of inactivity during the cold stuff. They are still batting about amongst their now medium-sized offspring and as Gill and Mark suggest, probably munching the odd one or two.
I had a similar fright last year with 100s of mini backswimmers, but only about 20 made it to adulthood.
M

[Dillybythesea]

Gosh Malcolm, even 20 sounds a lot! Our pond is only about 4m x 3m - so I hope that many don't make it through. Strangely I haven't seen any adults for several weeks so the tiddlers need to get on and eat each other! ATB, Dill

[Malcolm Banks]

Hi Dill, your pond sounds a little bit bigger than mine, and although in a new pond you may have flushes of species, in 18 months or so it should settle down so that the populations it supports are sustainable and in some sort of balance. Extreme weather might influence the balance to some extent, but in general you will end up with as many backswimmers as is sufficient for your pond. I had the same anxiety, because they are pretty voracious hunters, but I listened to advice on WAB and elsewhere, and by and large they had it right. If the backswimmers eat all the prey then they will die or fly off - must admit I like the concept of this horde of backswimmers decimating ponds and then flying off to decimate another one. Don't have nightmares!!
M