Ladybird: Rhyzobius chrysomeloides?

[Jason Green]

Evening all,

I was beating at a nice acid-grassland site today. I began working along an Oak/Hawthorn hedgerow and this dropped in. Being familiar with R. litura I was sure I was looking at another species.

I collected it and fortunately it was male. The genitalia matches images on the WCG site, the patterning is far darker than any such maculations on litura specimens I've seen and the ventral-margin to the pronotum is clearly curved - again, different to litura which is straight.

Three images - the setting micro-pinned voucher, pronotal view of sinuous ventral margin and the genitalia itself...

I believe I have the rare Rhyzobius chrysomeloides here, but just thought I'd seek any views on my determination here given it's status. Thanks for looking!

Take care,

Jason

[Klaas Reißmann]

Hi Jason,

it works without genitalia, because of the round habitus and the very strong rounded margins of the pronotum: Rhyzobius chrysomeloides.

Rhyzobius litura is more elongate in the habitus and the margins of the pronotum are more or less in line, just a little rounded so the pronotum appears smaller, more fine.

Regards
Klaas

[Jason Green]

Thanks Klaas. In the UK we seem to confirm these on genitalia, I've heard they're variable and certain characters subjective. Maybe it's because we've only recognised this as being in the UK since 1999 - perhaps it's just until we have enough experience to do it without dissection. Still, it's a great record for the site - it's also had the Chalcid wasp Brachymeria tibialis with only about six records since 1930 plus a coule of 'Notable' species to boot.

Here's the set-specimen once micro-staged; the appendages arranged European-style but micro-staged like flies and wasps. This has the advantage of easier ventral examination - this species has ventral characteristics separating it from litura.

[Klaas Reißmann]

Hi Jason,

Rhyzobius chrysomeloides is one of the most common species I know in my area. I have seen a lot of them. Rhyzobius litura is more rare and I only ind them by here an there, on sandy grounds and open graslands. But if you look at the beetles, they are steady in habitus, but very variable in colouring. So both of them are yellow-brownish, but the black markings are variable. They can be very small and separated into small dots, but they even can grow to just one big halfrounded black line colouring half of the elytra.

The difference in the margins of the pronotum are steady, although the differences in the habitus. But I have to admit, that the habitus is not very well for differenciation, because it is not very obviously and one needs to the a few beetles of each species to see it I even have my problems in seeing it when I didn't see them for a while.

I guess you will do very well after a little time and a few beetles.

Regards
Klaas

[Jason Green]

Thanks!

So litura is the less common of the two where you are? Conversely I find that to be a bit of a Beating-tray pest when beating low foliage!

Do you have any other Rhyzobius in Germany?

[Klaas Reißmann]

Hi Jason,

yes, Rhyzobius litura is a more or less rare species and I can approve that it is more often found in the grasslands by beating or dip neting, whereas R. chrysomeloides is absolutely common and can be found in the grasslands as well as in trees.

Most of all I found Rhyzobius chrysomeloides and for a few hundreds of R. chrysomeloides there might be one R. litura.

And we, too, have got only these two Rhyzobius-species.

Regards
Klaas

[htcdude]

Well done Jason on finding it!

Nige

[Jason Green]

Klaas, funny how it seems our Rhyzobius are that different to one another!

Thanks Nige, your comments are much appreciated