Identification of beetles (Coleoptera)

Potosia cuprina

Thank you, I think I came to this as well, but I still have my doubts.
S. I. Medvedev writes in the Fauna of the USSR that kuprins live in rotten wood, but I still got this one from the anthill

From the top left, it seems - Ilybius ater, to the right-Colymbetes ? paykulli. The bottom ones are large-Acilius female and male, look at the keys, there are two of them in total. I'd like to take a closer look at a small beetle.

Please help me identify these people. They are small. I need a microscope, but I don't have one yet.

Thank you very much.
I'll try Acilius using the keys myself.

Acilius (s) should be viewed from below. In A. sulcatus, the posterior thighs are darkened at the base, the first visible part of the abdomen (ventricle) is black, and the rest are only with yellow spots. However, the female has another reliable sign: the pronotum is on the sides with densely hairy depressions. And in A. canaliculatus, the hind thighs and this same ventritus ( ) are yellow. In the female, the pronotum is without hairy indentations, or they are barely noticeable. And besides these two species from Acilius, we have no one else.
By the way, these are still far from small swimmers. For them, an ordinary hand-held magnifying glass is enough, why a microscope? I would say very large ones. Here is Laccophilinae, Hydroporinae ( ) - this is yes!

I looked through many photos on the Internet on two Ditiskusam (M and S). And I noticed one feature. In Marginalis, both males and females, the posterior third of the elytra is translucent yellow , as if the black paint has worn off, but the Circumcinctus is completely black. Well painted. Can this be a sign for quick identification?

Who is it? Moscow, caught it yesterday.

Scanning the top view

No. 1 length 35 mm



No. 2 length 35 mm



No. 3 length 31 mm

D. marginalis

What? All three of them?
No way
But what about the appendages that are sharp and concave, like the dagger of a Dzhigit(the first one)?

Here:


It's not a joke to have such spikes!

Please identify the bug.

Thanks

I will try to fulfill my duty of honor (without quotation marks) to Irina.
Females of the two most frequent swimmers in the Moscow region:
1) Dytiscus marginalis marginalis Linnaeus, 1758
2) Dytiscus circumcinctus Ahrens, 1811

Vasily, you'd better move them to the topic of water beetles...
http://molbiol.ru/forums/index.php?showtop...0&#entry1005061

This elephant "came" to me yesterday.
Caught in January, Egypt, Nile Delta.
Can't you tell me anything about it?"

Some Lixus sp.

Please help me identify and decide. I suspect that all the photos of D. circumcinctus are male and female. After the photo of the front side, the underside of the same beetle is presented.

Is there a possibility to make basins closer? Do you have a scanner?
I'm also interested in seeing other examples

Dmitrich

Daps in my opinion trimaculata Motschulsky, 1835 or horvathi Csiki, 1901 - they are both genital