Dytiscidae - Scarodytes halensis?

[JRsbugs]

Hi,

Taken in my pond on 10th September 2009. The pond is new, filled towards the end of July and already thriving with pond life. It seems this is quite new to the UK with records mainly in the east midlands. Size 4-5mm.

I found some pics with the same markings, although those on the pronotum look to have merged on these all the patterns match up well. The only real difference I can see is the back legs on mine look to have stripes, but that doesn't always show.

Picture/photo of Scarodytes halensis (Scarodytes halensis) from Gørløse taken by Mogens Holmen - wildaboutdenmark.com

BioLib - Image - Scarodytes halensis

The nbn gateway distribution, for you Jason who thinks everything should be first in the south!

NBN Gateway - interactive species mapper

Janet

[JRsbugs]

I found a mention of this in Charles Darwin's records so it's been around a while! It is nationally scarce though, there is a record on the nbn just a few miles from me.

P192

http://darwin-online.org.uk/content/...text&pageseq=1

[Jason Green]

Morning Janet

Sorry, can't help with the ID - I'm not too familiar with the Dytiscidae family.

Originally Posted by JRsbugs

The nbn gateway distribution, for you Jason who thinks everything should be first in the south!

NBN Gateway - interactive species mapper

Thanks for that, I see it has a distribution in the South-east Coast. I wonder if that's where it was discovered?

I think it's a fair assumption that newcomers to the UK list should appear in the South first. Think about these...

Cream-streaked Ladybird, Harmonia 4-punctata (Suffolk, 1930s)
Harlequin Ladybird, Harmonia axyridis, (Essex in 2004)
Carnation Tortrix, Cacoecimorpha pronubana (South coast, 1905)
Light Brown Apple Moth, Epiphyas postvittana (Cornwall, 1930s)
Horse Chestnut Leaf-miner, Cameraria ohridella (SW London, 2002)
Plant bug, Arocatus roeselii (LNHM garden, March 2007)
Western Conifer Seed Bug, Leptoglossus occidentalis (South coast, 2008/09)
Southern Green Shieldbug, Nezara viridula (sites in South since 2003, mainly)
Plant bug, Deraeocoris flavilinea (South/central UK, 1996)
Southern Oak Bush Cricket, (Surrey, 2001)
Tachinid fly, Sturmia bella (Hampshire, 1999)
Tree Bumblebee, Bombus hypnorum (Wiltshire, 2001)
Dyctinid spider, Nigma walckenaeri (Kew? 1900s)
False Widow, Steatoda nobilis (Devon, 1879-ish)

I believe it's a fair assumption most, not all, newcomers arrive in the South first. Then spread in a lot of cases.

Nice shots by the way - it's not easy photographing something under the water's surface!

Take care,

Jason

[JRsbugs]

Thanks for that, I see it has a distribution in the South-east Coast. I wonder if that's where it was discovered?

OK smarty pants, I think in the past the relative short distance across the English Channel may have had a lot to do with 'first in the south'. In the last few decades things have changed dramatically! Oh, and don't forget there is a port at Hull (further north), as well as Folkestone (I know, a little further south!).

Consider :~ All the people who now travel by car to mainland Europe. I drove to Rome in the early 1990's, brought back 3 shield bugs in the car!

Consider :~ There's two nurseries only 4 and 5 miles by road from me, or closer as the crow flies, who have a fortnightly delivery from the nursery co-ops of Boskoop, Holland. I have seen a large container lorry pulling another large container trailer full of large plants going from one nursery to the other. I know that the nursery at Whisby (some will know that place!) also purchases bamboos from a grower in southern France.

Consider :~ All the deliveries now by lorry and road from Europe.

This all means to me much more likely sources of all sorts of insects crossing the channel and bypassing the south! Of course nurseries in the south may also purchase from the same places.

[Jason Green]

Afternoon Janet,

Originally Posted by JRsbugs

OK smarty pants, I think in the past the relative short distance across the English Channel may have had a lot to do with 'first in the south'. In the last few decades things have changed dramatically!

Just to clear something up, I don't mean 'First in the South' in a simple 'It was first in the South, then...' sense. These insects I mentioned were often imported, yes. The UK must get hundreds of alien insects imported per year though. I'm talking about those that are added to the UK list, establishments, etc - not just one or two individuals with produce that won't necessarily get on here.

Take Nigma walckenaeri for example. This spider was imported into Kew a whole century ago. In 100 yrs it has hardly exceeded the London and Home Counties area, though more recently has expanded slightly but is still very local. This says to me there are fairly specific things it needs, such as average temperature, suitable habitats, health and life of plants with concave leaves, etc. Such as, do suitable plants in warmer parts maybe have longer lives than others due to average annual temperatures, and so offer longer periods for breeding?

Not every bug that is seen in the UK as a new species can survive, even in the South - there have been far fewer records of the Southern Shield Bug than any previous years since it made it's debut here. It may be that the average temperature during winter, which is an important factor for newbies, down here is even too low for it.

Moth traps. There are several migrant non-UK moths caught each year, of course originating from the continent of their own accord. If they are going to become established, they first off need the Southern atmosphere to be suitable - temperature, food sources, over-wintering habitats, etc. If this suits them, they may then carry on further North. If not, they will remain maybe as Local southerners.

Dragonflies. The Small Red-eyed Damselfly came to the UK in 1999 through natural range expansion, probably to do with rising temperatures, etc. and has become established in the South, and having been satisfied with habitats, temperatures etc. is starting to spread North now.

What I'm saying is that a lot of, not all, insects that are going to become established in the UK, start off in the South, then spread. Obviously the more Northern ports you say could bring in new UK arrivals, and some may become established. These insects need more than just an entry into the UK - they need the habitat, food sources, temperatures for over-wintering, etc. when they get here in order to become established. All I'm saying is that initially in My experience the South is where most of the well-known new ones start out. Am I wrong? Tell me and I'll happily stand corrected

Anyway, I'm not having much luck finding anything much about Scarodytes halensis... any WIKIs or something? As I said, a nice series of shots

[charlieb]

Originally Posted by Jason Green

Anyway, I'm not having much luck finding anything much about Scarodytes halensis... any WIKIs or something? As I said, a nice series of shots

Synonyms are always a good place to start ... if you have the time - NBN Gateway - Search Results

[JRsbugs]

Originally Posted by charlieb

Synonyms are always a good place to start ... if you have the time - NBN Gateway - Search Results

Thanks for the synonyms Charlie, yes they are often a good way to find info. Strangely the name 'preferred' is actually an incorrect form.

Thanks Jason, it was stuck to a root of the duckweed and seemed to be having truoble getting away from it! I released it and it went under the duckweed, after taking pics! You can see how the root is held down by the tiny mite, not sure if it stayed on but I had a pic showing the beetle half under the duckweed and deleted it! I haven't tried finding out the name of the mite yet, it might prove difficult but if anyone has a clue let us know please.

It seems Jason has plenty of time to check out the synonyms, lol, all true what you have said though Jason but somehow understood by those who understand anyway.

I found the last link on the last (3rd page) of a google which gives some info of studies done in Germany.

Nutritional and ecological studies on pioneer species (Coleoptera, Hydradephaga Dytiscidae) in sandpit ponds. | Kehl, S., Dettner, K. | Mitteilungen der Deutschen Gesellschaft für allgemeine und angewandte Entomologie | Deutsche Gesellschaft für al