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Saucer Bug, Ilyocoris cimicoides
enlarge Saucer bug
Ilyocoris cimicoides
Head and front legs
head Ilyocoris cimicoides
GOOD CHANCE YOU FIND A FEW OF THIS BUGS in your dipping net after one single scoop, provided the ditch has enough water plants. They are not as common as the Lesser water boatmen and backswimmers, but in some waters they swarm. Yet you may not see them at first: Saucer bugs are shy and hide in the water plants. But they are very good swimmers, and when swimming look like water beetles with a dark back and a silver shimmering underside, because of a small sheet of air on the abdomen.
Saucer bug top view
At the surface

Hind leg Saucer bug, Ilyocoris cimicoides
When he's out of the water the Saucer bug is able to walk well, in the pond net he crawls quickly, sliding as if it were, under some leaves or in a safe corner. This bug needs some supporting vegetation in the water, because though the insect is able to refresh it's air supply by bringing the tip of the abdomen to the surface like a diving beetle , the Saucer bug cannot keep a stable position there, as those beetles can. That's why this bug dangles rather awkwardly below the surface in your jar with pond water, after swimming round panicky. Add some plants or sticks and he is much more comfortable. Even more so in a small aquarium with ground and plants, where Ilyocoris clings to the bottom, that is if he doesn't crawl away between the vegetation. Now we can take a closer look.

APPEARANCE Seen from above the shape of the body is oval, but in side view it is rather flat, like that of many bugs. Many people feel an instinctive repulsion against flat insects. If we can overcome that, we find this bug is beautifully adapted to its life habits. The underside has a layer of short hairs which hold a sheet of air when under water. This air layer, which renders a silvery glimmer to the abdomen, is part of the breathing air supply for the insect - though some investigators think it's just there for a hydrostatic balance, a bit like the swim bladder of a fish. There's another supply of air: the space between the elytra (hardened wings) and the abdomen. The hind legs have broad fringes of swimming hairs that yield more power by creating a larger surface, they provide the animal with two powerful paddles. The head is streamlined with a smooth, round shape. The eyes seem to give the insect an aggressive expression. The front legs are remarkable, they have the appearance of the scissors of a lobster. The femur ("thigh") is broadened by the powerful muscles within and has a groove. The tibia and tarsus(foot) are merged to a single claw, that can be pressed in the groove to form a merciless trap. The grim purpose of this construction may be clear: a small animal that gets caught in these sharp claws will never escape alive. The front legs look much like the deadly sucking jaws of the larva of the great diving beetle. But the claws of the Saucer bug are not hollow, and not used for sucking out it's prey, instead it stabs its razor sharp beak in them, then toxic digestive saliva is injected in the wound, after which the dissolved body parts are sucked in. This process is continuously repeated during the feeding process. In a human finger this toxic injection needle may also penetrate deep. Many investigators felt it was worse than the sting of a wasp, yet others wrote that the pain is intense, but short. Under the elytra, the outer wings or front wings, all Saucer bugs have hind wings of normal length. Whether they are able to fly is not certain. The wings may also have a function in sealing the airspace between the elytra and the abdomen. In spring the males seem to be able to produce tones with there abdomen. After mating, during which the male sits in a slanted left position on the female, the eggs are injected in water plants. That makes them difficult to find.

The nymph
Saucer bug nymph (Ilyocoris cimicoides)
enlarge Saucer bug nymph
Saucer bug nymph below water surface
enlarge Below the surface
As with all Hemipterae (bugs) the nymph already closely resembles the perfect insect. It has no wings and is rather transparent. The bright red eyes, contrasting with the light green body make it look a bit more attractive. Of course is it as predaceous as the adult Saucer bug. Yet I've never seen one catch a suitable prey, even if it was right under there beak. Could it be they only hunt in the dark? They are rather vulnerable as well: in the aquarium they often died after a few days, even though there was plenty of food. The nymphs are flatter and more transparent then the full grown Saucer bug. On the picture on the right you can see the transparent body. Clicking on that picture will show you an enlargement and some more pictures of this specimen.

The scientific name for the Sauce bug is Ilyocoris cimicoides, sometimes you may find the older name Naucoris cimicoides which is now discontinued.

Notes and web links:
1) Naucoris maculatus is another species in Europe, distinguished by four dark stripes on the neck shield.
2) The head looks like an source of inspiration for car designers.
3) Great source for old literature. (University of Göttingen)
4) Aphelocheirus aestivalis, sometimes called "the Creeping Water bug" was seen as a relative in former times. But it has proven a totally different type of bug.

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All pictures on this site were made by Gerard Visser (Aadorp, Netherlands), unless stated otherwise. All rights remain with him. These pictures may not be used for purposes any other than private viewing or printing. Do NOT hardlink to these pictures or place them on other websites without the author's approval. Should you need them for purposes which include third parties, you must ask the author permission by e-mail. People, who want to use this pictures for exhibitions or publications or educative material are much encouraged to do so, after approval as mentioned and giving the normal credits.
© G.H. Visser 30-04-2008
rev. 17-08-2011

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