The Squeak beetle is often said to be found in the mud, but I usually found this species on sandy bottoms, where there was a thin layer of muddy detritus. This male specimen was one of them, which was in the same recreational pond as the female specimen on the next page a few years earlier. The beetle dives into the sandy bottom until only the air bubble at its rear end is visible. If you gently (but firmly) push an upside-down jam jar full of water around it, you usually manage to catch it.

Squeak: If this beetle gets caught in your pond net, you'll often notice it by the peculiar creaking sound it makes. You'll also hear these sounds if you try to take photos and the beetle becomes restless. In English descriptions, you'll find the names "Screech Beetle" or "Squeak Beetle." Click on the audio player triangles below to hear a few audio recordings of this specimen.

The sound, stridulation, is produced by the rubbing of the abdomen against the elytra and may serve as a deterrent to potential predators. I can also be startled by the sudden grinding sound, even if it's soft. Bilton & Blair (2020) cite several studies showing that insects that make this kind of deterrent noise had a greater chance of escape.

This remarkable beetle belongs to a separate family, the Hygrobiidae or Paelobiidae, which is usually considered a relict. Hygrobia is the only genus in this family, of which five species are known: one in Europe and England, two in China and Tibet, and two in Australia (Wesenberg Lund, 1943; Cuppen, 2000).

Like the Dytiscidae, the Squeak beetle takes in air at the water's surface with the tip of its abdomen, then swims downwards with an air bubble attached to that tip. It has swimming hairs on all its legs, but it swims "kicking": with alternating, not paired, strokes of its hind legs. This causes the beetle to sway slightly through the water with its rounded body and it is not as fast as the streamlined aquatic predatory beetles. Nevertheless, the impression is more that of a fast-moving and nervous beetle than a sluggish insect. Like most aquatic beetles, the Squeak beetle ascends effortlessly, but must swim downwards with force because the air bubble makes it lighter than water.

I've never seen these beetles resting with their hind ends "hanging" at the water's surface, like the Great divingbeetle, for example. The Squeak beetle probably can't do that; in the large photo above, the beetle is partially floating with its head and thorax on the water, creating distracting glare. I also saw this happen constantly with the female specimen I photographed years earlier. Of course, the beetle can easily breathe air; in the picture on the left, you can see how the tip of the abdomen opens at the water's surface, similar to a water-dwelling beetle. But you never see the hindlegclaw-abdomentip "support triangle" of the Dytiscidae here; the claws are apparently not equipped for this, and/or the hind legs cannot assume the necessary upright position.

Below is a photo of a rare moment of a calm beetle on the bottom. The water is still cloudy from the swirling sand.

The antennae are long, like those of the Dytiscidae. However, the eyes are much more prominent than those of these beetles. The jaws are large and sharply pointed: Hygrobia eats small worms and Chironomid larvae (Cuppen, 2000). All legs are equipped with swimming hairs.

The photos above give a glimpse of the beetle as it burrows. The air bubble at its rear end connects to the air beneath its elytra, allowing the beetle to ventilate its tracheae through the stigmata on top of its abdomen. In the right-hand photo, a section of the abdomen protrudes above the sand. Hover the mouse over that right-hand photo to switch between two shots from (more or less) the same vantage point, and you'll see how the bubble can expand and contract. Like many Dytiscidae, the Squeak beetle does this to promote gas diffusion between the water and the bubble: the so-called "physical gill." It can remain submerged for at least half an hour, and can draw air from the surface in 5 to 10 seconds (Dettner, 1997). This allows the beetle to remain well out of sight.

As previously described, Hygrobia often burrows completely under the sand, until only the air bubble at its rear end is visible. You can see this in the photo above. This behavior isn't peculiar, since its food, Chironomid larvae and worms, is also found somewhat deeper in the soil. Moreover, it may go unnoticed by a heron or other animal that eats beetles.

This shy behavior makes taking a good, natural photo nearly impossible. On the right, you can see the beetle effortlessly rising from the sand: at that moment, it's lighter than water.

About the sound. On the left is a drawing by Balfour-Browne (1922) of the underside of the right elytron. In it, he has marked a strip of toothed ridges at the bottom as a "File," noting that the left elytron also has a similar stripe. The following is based on an article by Bilton & Blair (2020, Plymouth University). They investigated, among other things, the frequency and structure of the sound-producing components. Both males and females produce the characteristic sound. The grinding sound is produced by rubbing the last segment of the abdomen (the "plectrum") forward and backward against the strips of toothed ridges on the underside of the posterior part of the elytra (the pars stridens). The researchers found similar plectra but subtly different pars stridens in males and females: somewhat wider toothed ridges.
The peak frequency of the sound was 6.1 kHz. The creaking sounds changed during the study period, more so in males than in females. The researchers suggest that this could mean that, in addition to their deterrent effect, the sounds may also have an intra-communicative function.

Balfour-Browne (1922) wrote that when a Screech beetle tried to seize a piece of worm already in the possession of another of its kind, the latter made a crunching sound, "...presumably being equivalent to the growl of a dog with a bone".

Westra (1967), who kept several Squeak beetles together in an aquarium, wrote: "It's as if they warn each other with their creaking noises that danger is approaching." This was also because he often found several specimens together, in "...a very limited, sharply defined section of the bottom surface...". I myself once caught three squeaky beetles with a single stroke of the net in a small pool.

Locations. Westra (1967) states that they are never found in ditches, but on sandy soil in shallow, well-vegetated ponds with a muddy bottom and 30-50 cm of water. The two beetles on this website, which I caught years apart, were in a larger recreational pond, albeit at the edge, where the depth was a good half meter. All other Screech beetles I caught in the ponds characterized by Westra (1967). Balfour-Browne (1922) also never found the beetles in ditches or streams, but "...in ponds where the bottom is covered with a fine “ooze”, so that gravel- or marl-pits are ideal habitats" - this seems consistent with my own findings in the recreational pond. However, in Cuppen's (2000) study, Screech beetles were also found in ditches and on clay soil, and the water type seemed less important.

"What's in a name":

Dutch names. This beetle is listed in the Dutch species register under the rather unappealing name "slijkzwemmer" (mire swimmer), but various sources also list it as "modderkever" (mud beetle). These names refer to the beetle's location and behavior, as described, although the substrate can also be sandy. The more appealing name is 'pieptor' (pronuncation: as peep, phoneticaly: /pi:p tɔ<r>/), which means the same as the English Squeak beetle.

The scientific name, the oldest I could find, was Dytiscus hermanni Fabricius 1775. In the edition of Linnaeus' Systema Naturae mentioned below , I also came across that name (with a capital H), but under that monograph, the beetle was also referred to as the Dytiscus tardus, described by J.W.F. Herbst. The "slow diver" - bit of an exaggeration: the Squeak beetle isn't as fast as a Great diving beetle, but it's still difficult to catch with a small net! The species designation hermanni ("from "Hermann"") was a tribute to the French researcher Johann Hermann

On another page of this website, you can read that the genus name Dytiscus was initially used for (too) many species of water beetles. In the following paragraph, I present my interpretation of an article by Nilsson (2006). Various entomologists gave different names to the beetle. The Dane Johann Fabricius provided the oldest description of the beetle in 1775 as Dytiscus hermanni. Later, in 1801, he began adjusting the large Dytiscus group by placing the Squeak beetle and a few other species in a group he coined, Hydrachna ("water spider"). However, that name was already taken by a group of watermites, so it was incorrect. The Frenchman Latreille eventually changed the genus name to Hygrobia, but the Swede Schönherr, who may have been unaware of this, coined the genus Paelobius, using Herbst's synonymous tardus species name for the Squeak beetle! The German Erichson later changed Paelobius to Pelobius, which was not according to the rules. The names Hygrobia hermanni and Pelobius tardus were both in use for a very long time, and I also came across the names Pelobius hermanni and Hygrobia tardus. At the time of writing, the common name is still Hygrobia hermanni (Fabricius 1775), the author's name in parentheses due to the genus change. The family in which Hygrobia is included as the only genus is called Hygrobiidae, but according to Nilsson (2006), Paelobiidae would be a more correct older name.

Literature (Zie ook: Bibliography of water beetles ), and Wikipedia.

Balfour-Browne, F. 1922 The Life-History of the Water-Beetle Pelobius tardus Herbst. Proceedings of the Zoological Society of London 1922 79-97, (illustrations between page 78 en 79) Vitty & Seaborne, ltd., London
BHL scan can be found at: "https://www.biodiversitylibrary.org/item/100598#page/116/mode/1up"
DOI "https://doi.org/10.1111/j.1096-3642.1922.tb03300.x"
Article (composed by BHL) retrieved 4 nov 2025 from "https://www.biodiversitylibrary.org/item/100598"

Bilton, D. & Blair, J. 2020 The call of the squeak beetle: bioacoustics of Hygrobia hermanni (Fabricius, 1775) revisited (Coleoptera: Hygrobiidae) Aquatic Insects, , pp. 1-14. Retrieved from: https://pearl.plymouth.ac.uk/cgi/viewcontent.cgi?article=1200&context=bms-research

Bilton, D. & Blair, J. 2019 The call of the squeak beetle: bioacoustics of Hygrobia hermanni (Fabricius, Citation1775) revisited (Coleoptera: Hygrobiidae) Aquatic Insects, 41(2), 131 - 144
Read the excerpt, 25 oct 2025 at "https://www.tandfonline.com/doi/full/10.1080/01650424.2020.1726963?scroll=top&needAccess=true&" (DOI: https://doi.org/10.1080/01650424.2020.1726963)

Cuppen, J. 2000 Distribution, phenology, food and habitat of Hygrobia hermanni in The Netherlands (Coleoptera: Hygrobiidae). Ent. Ber., Amsterdam. 60 (4): 53-60.
Retrieved 25 oct 2025 from "https://edepot.wur.nl/573111"

Dettner,K. 1997 Insecta: Coleoptera: Hygrobiidae Süßwasserfauna von Mitteleuropa 20/2,3,4 Gustav Fischer 1997
PDF retrieved 4 nov 2025 from "https://www.researchgate.net/publication/305618564"

Hemming, F., (secretary) 1954 - Opinion 280: Emendation to Hygrobia of the generic name Hygriobia Latreille, 1804 (Class Insecta, Order Coleoptera - Opinions and declarations rendered by the International Commission on Zoological Nomenclature 6 part 12 189-204
Retrieved 25 oct 2025 from "https://ia802802.us.archive.org/25/items/biostor-146248/biostor-146248.pdf".

Linné, C. 1788-1793 Systema naturae per regna tria naturae : secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis Tomos I Part IV 1949
Lipsiae [Leipzig], Impensis Georg. Emanuel. Beer, 1788-1793
Retrieved 25 oct 2025 from "https://www.biodiversitylibrary.org/item/10288#page/433/mode/1up"

Nilsson, A. 2006 Which name is valid - Hygrobiidae or Paelobiidae? Latissimus, Vol. 21, p. 37-39 - 2006 Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.(I did not yet read this article!)

Nilsson, A. 2005 Family Paelobiidae (Coleoptera, Adephaga) - In Nilsson, A.N. & Vondel, B.J. van. 2005. Amphizoidae, Aspidytidae, Haliplidae, Noteridae and Paelobiidae (Coleoptera, Adephaga). - World Catalogue of Insects 7: 1-171.
Excerpt retrieved 25 oct 2025 van "https://brill.com/display/book/9789004473393/B9789004473393_s007.xml"

Schreijer, M. 1992, Hygrobiidae (Pieptorren) - In M.B.P. Drost, H.P.J. Cuppen, E.J. van Nieukerken, A.M. Schreijer, (red.) 1992. De waterkevers van Nederland 89. - Uitgeverij K.N.N.V., Utrecht.

Wesenberg Lund,C. (1943) "Pelobiidae (Hygrobiidae)" Biologie der Süsswasserinsekten p. 311 Publisher: Verlag J. Springer, Berlin-Vienna 1943

Westra, H., 1967 Hygrobia hermanni Ol., het modderkevertje (Col., Hygrobiidae) Entom.ber. 27, 1 11 1967
Excerpt bought at Kabourek s.r.o. Zlin (CZ) feb 2021, also retrieved the pdf 25 october 2025 from
"https://natuurtijdschriften.nl/pub/1013943/EB1967027002004.pdf"