# Predaceous Diving Beetles (*Dytiscidae*)

Predaceous diving beetles are amazing swimmers! They have shiny bodies and can dive underwater to catch their food. These little bugs are like superheroes of the pond!

- **Category:** [Insects](https://www.snappit.app/explore/categories/insect)
- **Rarity:** Common
- **Danger:** 1/5 · Very low
- **Habitat:** Wetlands

![Predaceous Diving Beetles](https://commons.wikimedia.org/w/index.php?title=Special:Redirect/file/Geelgerande01.jpg&width=800)

Photo: User Evanherk on en.wikipedia, Public domain · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Geelgerande01.jpg)

## Appearance

The Predaceous Diving Beetles have sleek, oval-shaped bodies that are usually dark brown or black, often with yellow or reddish markings. Their smooth, hydrodynamic shell helps them glide easily through water. They possess large eyes adapted for underwater vision.

## Taxonomy

- **Kingdom:** Animalia
- **Phylum:** Arthropoda
- **Class:** Insecta
- **Order:** Coleoptera
- **Family:** Dytiscidae

## Diving beetles, up close

Predaceous diving beetles (family Dytiscidae) are a worldwide family of more than 4,000 water beetles that hunt in ponds, lakes, streams and even underground waters. Adults carry a store of air under their hard wing cases and row with flattened, hair-fringed hind legs, while their long, thin larvae, nicknamed “water tigers”, ambush prey with hollow, sickle-shaped jaws. The great diving beetle (Dytiscus marginalis) of Europe and northern Asia, 27–35 mm long, is one of the best known.

Also called: Diving beetles, Predacious diving beetles, Predaceous water beetles, Dytiscids, Water tigers (the larvae).

Pond hunters that carry their own air tank, row with hairy oar legs and fly off to new ponds. Their larvae are the “water tigers”. Spin one, tap it, then test yourself.

### Special abilities

- **Twin-Oar Stroke** (12.9 cm/s top forward speed in one stroke): Diving beetles row with their two flat, hairy hind legs, pushing both at the same time. They can even swim backwards without turning round. [8][13][7]
  - In high-speed films of Cybister bengalensis, a 36 mm beetle, forward speed peaked at 12.9 cm/s during a stroke and averaged 8.74 cm/s.
  - Swimming backwards, probably to escape danger, it went from 0 to 27.3 cm/s in just 50 milliseconds.
  - The legs push hard on the power stroke and meet little resistance on the way back. Computer flow models gave a forward efficiency of 0.47.
  - Cybister bengalensis swimming speeds: Backwards escape burst 27.3 cm/s; Forward, fastest moment 12.9 cm/s; Forward, average 8.74 cm/s
- **Scuba Bubble** (minutes–24 h per dive, depending on species): Before diving, the beetle tops up the air store under its wing cases by touching the surface with the tip of its abdomen. Then it can stay under for minutes or hours. [5][2][6][14]
  - Dives last from a few minutes to 24 hours, depending on the species, how active the beetle is and the water temperature.
  - A small bubble at the tail tip acts as a physical gill, pulling a little extra oxygen in from the water.
  - One stream-living species, Deronectes aubei, survived more than 6 weeks without surfacing, and some beetles in underground waters in Australia breathe through their skin.
- **Hidden Wings** (2 pairs of wings: hard cases and flight wings): Under the hard wing cases sit two things a swimmer needs: a pocket of air to breathe and a pair of folded flight wings for leaving the pond. [5][2][1]
  - The wing cases are the beetle’s front wings, hardened into a shell. They seal in the air store.
  - The thin back wings fold away underneath when the beetle swims and open out when it flies.
  - The air store is refilled at the surface through the gap at the tip of the abdomen.
- **Pond Hopper** (99 kinds of water insect studied in flight): Diving beetles climb out, open their wings and fly to new ponds. They find water by its shiny, polarised glare, which can fool them into landing on cars. [15][1][10]
  - A study of 99 kinds of flying water insects (78 of them beetles) found that they fly mainly in mid-morning, around noon or at nightfall, depending on the species.
  - The great diving beetle is said to fly mostly at night.
  - Shiny red and black car roofs reflect light like a pond does, so water beetles sometimes land on them by mistake.
- **Suction-Cup Grip** (3 large cups per front foot in Acilius males): Male diving beetles have front feet like suction pads to hold on to a female under water. Females in many species have grooved wing cases that make them hard to grip. [3][4][9][16]
  - Charles Darwin used male and female diving beetles as an example in his work on differences between the sexes.
  - A 2007 study found that each new female surface that weakens the grip is matched by changes in the males’ suction cups: an evolutionary tug of war.
  - Some species have two kinds of female, one rough and one smooth. Tests showed the cups stick less well to the rough kind.
- **Steroid Squirt** (≈50% of the sunburst beetle’s defence volatiles are one steroid): When grabbed, diving beetles ooze a milky defence fluid from glands behind the head, and another secretion from glands at the tail tip. [17][2][18]
  - The sunburst diving beetle’s milky fluid is mostly steroids: one, mirasorvone, makes up about 50% of the volatile chemicals and cybisterone about 20%.
  - Mirasorvone was the first steroid of its kind found in any insect.
  - Scientists think the steroids can make a fish spit the beetle back out. Glands at the tail tip make a second, different secretion.
- **Water Tiger Sip** (15 s to catch a moving tadpole): The larva grabs prey with hollow, curved jaws, sends digestive juice in through them and then sips the softened food back out. [19][2][20]
  - Each jaw has a fine channel that opens near the tip. The larva digests its meal outside its body, then drinks it.
  - Movement switches on the attack: larvae caught swimming tadpoles in about 15 seconds but took about 120 seconds over still ones.
  - Larvae of the Japanese Dytiscus sharpi prefer to hold a tadpole by its belly, the most nourishing part.
- **Winter Under Ice** (below 8 °C winter cold needed to ripen eggs (D. sharpi)): Many diving beetles stay active in cold water all winter, even under the ice. Some species actually need the cold to breed. [21][22]
  - In Nova Scotia, Canada, the diving beetle Laccophilus maculosus stays active all year, including in ice-covered ponds (2026 study, not yet peer reviewed).
  - Dytiscus sharpi in Japan starts mating when the water drops below 20 °C, mostly in November and December.
  - Its females only ripen their eggs after a winter below 8 °C, then lay them in spring.
  - Temperature switches in Dytiscus sharpi: Mating starts below 20 °C; Eggs ripen after winter below 8 °C

### Body parts

- **Wing cases** (27–35 mm great diving beetle length) [1][2][3][4]
  - The hard front wings, called elytra, close over the back like a smooth, streamlined shell. Head, thorax and abdomen fit together into one oval.
  - In the great diving beetle, a yellow rim runs around the shield behind the head (the pronotum) and along the wing cases.
  - Males have smooth wing cases. In many species the females have grooves or a rough surface instead, which makes it harder for a male’s suction cups to hold on.
- **Under the wing cases** (up to 24 h on one air store, depending on species) [5][2][1]
  - Between the wing cases and the abdomen is a space filled with air. The beetle breathes from it through small holes in its sides called spiracles.
  - It refills the store at the surface, then dives again. Depending on the species, how active it is and how warm the water is, a dive lasts from a few minutes to 24 hours.
  - The see-through flight wings are folded underneath too, ready for flying to a new pond.
- **Air bubble** (8× longest dive extension a bubble gill could give, in theory) [2][6]
  - A small bubble is often pushed out from under the wing cases and held at the tip of the abdomen by water-repelling hairs.
  - The bubble works as a “physical gill”: as the beetle uses up its oxygen, more oxygen seeps in from the water.
  - Models say this could make a dive more than 8 times longer, but real insects come up for fresh air long before the bubble runs out.
- **Hind legs** (≈80% of body length (Cybister)) [7][8]
  - The hind legs are long, flat and fringed with stiff hairs, so they work like a pair of oars.
  - Big diving beetles stroke both hind legs at the same time, like a rower, rather than one after the other.
  - In the Asian diving beetle Cybister bengalensis, each hind leg is about 80% as long as the whole body.
- **Front feet** (3 large suction cups on each front foot (Acilius males)) [3][1][9]
  - In males of many large diving beetles, the front feet are widened into round pads covered in tiny suction cups. In the great diving beetle the middle feet have some too.
  - Males use them to hold on to a female’s back during mating, under water.
  - In the genus Acilius, each male front foot has 3 large cups and many tiny ones. Round, later-evolved sucker hairs grip better than older spatula-shaped ones.
- **Eyes** [10][11][12]
  - Flying diving beetles find water by looking for shiny surfaces that reflect light in a special, flat-lying (horizontally polarised) way, as ponds do.
  - That is why they sometimes land on shiny red or black cars, which reflect light in the same way. Yellow and white cars do not fool them.
  - The larvae of the sunburst diving beetle have some of the strangest eyes known: their main eyes have bifocal lenses with two retinas, a little like reading glasses.
- **Antennae** (up to 11 segments) [2]
  - Diving beetle antennae are long and thread-like, usually longer than the head is wide, with up to 11 segments.
  - This is a quick way to tell them from water scavenger beetles and whirligig beetles, whose antennae end in a club.
  - They are smooth and bare: scientists call them glabrous.
- **Jaws** [2]
  - Adults have strong jaws (mandibles). They bite off and swallow small pieces of their food.
  - They eat live animals and also clean up dead ones, so they are both hunters and scavengers of the pond.
  - If picked up, a big diving beetle can give a sharp nip. Watch it in the water instead of handling it.

### Stats

| Stat | Value | Notes |
|---|---|---|
| Species | 4,200+ | described worldwide, in almost every kind of fresh water; water beetles of all families add up to more than 13,000 [23][2][24] |
| Great diving beetle | 27–35 mm | adult length of Dytiscus marginalis [1] |
| Water tiger | up to 60 mm | a fully grown great diving beetle larva, longer than the adult [1] |
| Biggest in Europe | 44 mm | Dytiscus latissimus, a protected species [25][1] |
| Smallest | ≈0.9 mm | Limbodessus atypicali, from underground waters in Australia [2] |
| Top forward speed | 12.9 cm/s | peak of one stroke, Cybister bengalensis [8] |
| Escape burst | 0–27.3 cm/s | swimming backwards, in 50 milliseconds [8] |
| Time under water | minutes–24 h | per air store; one stream species lasted over 6 weeks [5] |
| Hind-leg length | ≈80% | of body length in Cybister bengalensis [8] |
| Rowing efficiency | 0.47 | forwards (0.30 backwards), from computer flow models [13] |

### Photos

- [A great diving beetle in Finland: note the yellow rim](https://commons.wikimedia.org/wiki/File:Dytiscus_marginalis_from_finland.jpg) (photo: Thintkk, CC BY-SA 4.0)
- [A female great diving beetle, with grooved wing cases](https://commons.wikimedia.org/wiki/File:Gewone_geelgerande.jpg) (photo: Bram Koese, CC BY-SA 4.0)
- [A water tiger: great diving beetle larva in Berlin](https://commons.wikimedia.org/wiki/File:Dytiscus_marginalis_larva_in_the_Teufelsbruch_01.jpg) (photo: Leonhard Lenz, CC BY-SA 4.0)
- [Hanging from the surface by its breathing tube, waiting for prey](https://commons.wikimedia.org/wiki/File:Dytiscus_marginalis_larva.jpg) (photo: Hulcr, CC BY-SA 4.0)
- [Sunburst diving beetle at Cincinnati Zoo](https://commons.wikimedia.org/wiki/File:Sunburst_Diving_Beetle_049.jpg) (photo: Ltshears, CC BY-SA 3.0)
- [Sunburst diving beetle photographed in Mexico](https://commons.wikimedia.org/wiki/File:Thermonectus_marmoratus_(Dytiscidae)%2C_escarabajo_buceador_0001.jpg) (photo: Juan Carlos Fonseca Mata, CC BY-SA 4.0)
- [A great diving beetle in southern France](https://commons.wikimedia.org/wiki/File:Great_Diving_Beetle_(Dytiscus_marginalis)_(8332211239).jpg) (photo: Bernard DUPONT, CC BY-SA 2.0)
- [A great diving beetle near Begunitsy, Russia](https://commons.wikimedia.org/wiki/File:%D0%91%D0%B5%D0%B3%D1%83%D0%BD%D0%B8%D1%86%D1%8B%2C_%D0%BF%D0%BB%D0%B0%D0%B2%D1%83%D0%BD%D0%B5%D1%86_%D0%BE%D0%BA%D0%B0%D0%B9%D0%BC%D0%BB%D1%91%D0%BD%D0%BD%D1%8B%D0%B9.jpg) (photo: Nikolay Bulykin (Красный), CC BY-SA 4.0)
- [Dytiscus latissimus pair: male on the right, female on the left](https://commons.wikimedia.org/wiki/File:%E3%82%AA%E3%82%A6%E3%82%B5%E3%83%9E%E3%82%B2%E3%83%B3%E3%82%B4%E3%83%AD%E3%82%A6%E3%83%A2%E3%83%89%E3%82%AD_%E3%83%9A%E3%82%A2.jpg) (photo: Ikaruga1127, CC BY-SA 4.0)

### Questions

- **Do diving beetles bite?** They can. Big diving beetles have strong jaws and may give a sharp nip if picked up, and they also ooze a defence fluid. Watch them in the water instead of handling them, and tell an adult if you get nipped. [2][17]
- **How do diving beetles breathe underwater?** They carry air. Adults keep a store of air under their wing cases and refill it at the surface, tail first. A small bubble at the tail tip also draws a little oxygen from the water, like a simple gill. Larvae breathe through a tube at their tail tip. [5][6][2]
- **How long can a diving beetle stay underwater?** From a few minutes to about 24 hours on one air store, depending on the species, how active it is and how warm the water is. A few stream and underground species hardly need to surface at all. [5][14]
- **Can diving beetles fly?** Yes. They have folded flight wings under their wing cases and fly to new ponds, usually at set times such as mid-morning, around noon or at nightfall. They spot water by its shine, and sometimes land on shiny cars by mistake. [15][10][1]
- **Why are diving beetle larvae called water tigers?** Because they are fierce hunters. A larva grabs prey with its hollow, curved jaws, sends digestive juice into it and then sips up the softened food. It attacks things that move, such as tadpoles and insect larvae. [2][19][20]
- **What do diving beetles eat?** Small water animals such as insect larvae (including mosquito larvae), tadpoles and small fish. Adults also eat dead animals, which helps keep ponds clean. [2][1][26]
- **How big do diving beetles get?** Most are 1–2.5 cm long. The great diving beetle reaches 27–35 mm, Europe’s biggest, Dytiscus latissimus, about 44 mm, and the smallest known species is about 0.9 mm. [2][1][25]
- **Are diving beetles endangered?** Most species are common or have never been assessed. But Dytiscus latissimus and Graphoderus bilineatus are Vulnerable and protected in the EU, and Brazil’s giant Megadytes ducalis is listed as Extinct. [32][36][29][25]

### Diving beetle myths and facts

Tap Myth or Fact for each claim, then check the answer.

- "Diving beetles breathe under water with gills, like fish." **Myth!** Adults breathe air. They carry a store of it under their wing cases and refill it at the surface. A bubble at the tail tip helps a little by drawing oxygen from the water, but it is not a real gill. [5][6][2]
- "Some diving beetles can stay under water for a whole day." **Fact!** Dives last from a few minutes to 24 hours, depending on the species, activity and temperature. One stream species stayed under for more than 6 weeks. [5]
- "Diving beetles can fly." **Fact!** Folded flight wings sit under the wing cases. Water beetles fly to new ponds, mostly in mid-morning, around noon or at nightfall. [15][1]
- "Diving beetles sometimes mistake cars for ponds." **Fact!** Shiny red and black cars reflect light in the same flat, polarised way as water, so flying water beetles land on them. [10]
- "Water tigers chew up their food and swallow it in chunks." **Myth!** The larvae push digestive juice into their prey through channels in their jaws, then suck up the softened food. Adults are the ones that bite off pieces. [19][2]
- "Diving beetles survive being frozen solid in the ice." **Not proven!** Many stay active in cold water under the ice all winter. But we found no study showing that they survive being frozen solid. [21][22]
- "All diving beetles are big." **Myth!** Most are 1–2.5 cm long. The smallest is about 0.9 mm, while Europe’s biggest, Dytiscus latissimus, reaches 44 mm. [2][25]
- "Diving beetles eat mosquito larvae." **Fact!** Both larvae and adults eat mosquito larvae. Whether they can keep mosquito numbers down is less certain, and scientists are still testing it. [26][27]

### Diving beetle records

Superlatives and record holders, each checked against its source.

- Largest diving beetle: Megadytes ducalis (Brazil), ≈4.75 cm (known only from 11 museum specimens collected in the 1800s, and listed as Extinct) [28][2][29]
- Biggest in Europe: Dytiscus latissimus, 44 mm (one of the largest diving beetles in the world, and protected across the EU) [25]
- Smallest: Limbodessus atypicali (Australia), ≈0.9 mm (lives in underground waters (aquifers)) [2]
- Longest time submerged: Deronectes aubei, 6+ weeks (a stream beetle that takes oxygen from the water through special hairs) [5]
- Fastest getaway: Cybister bengalensis, 0–27.3 cm/s (swimming backwards in 50 milliseconds) [8]
- Bifocal eyes: Sunburst diving beetle larva, 1st (first living animal shown to have truly bifocal lenses (before, only suggested for some trilobites)) [11]

### The life of a diving beetle

From an egg hidden in a plant stem to a flying adult, with a stop on dry land in between.

- **Spring**: Eggs in a stem. Females of Dytiscus and Cybister lay their eggs inside the stems of water plants, below the surface. Cybister females bite a hole in the stem first. [30]
- **Hatching**: Out of the stem. Each tiny larva has to wriggle out through a crack or hole in the stem and swim up to the surface to take its first breath. [30]
- **Weeks of growing**: Water tiger. The larva hunts tadpoles, insect larvae and other small animals, breathing through a tube at its tail tip. It sheds its skin as it grows. [19][2][26][12]
- **Fully grown**: Up onto the bank. The big larva crawls out of the water and buries itself in mud on the bank. There it changes into a pupa. [2]
- **Adult**: Back to the water. The new adult returns to the pond. Great diving beetles grow to 27–35 mm. [2][1]
- **Any time**: Flying to new ponds. Adults can fly off to find new water, often at certain times of day such as mid-morning or nightfall. [15]
- **Autumn and winter**: Cold-water breeding. Some species mate in late autumn and stay active under the ice. Dytiscus sharpi needs a cold winter before its eggs ripen. [22][21]
- **Years**: A long life for a beetle. Some species live for several years as adults. [2]

### Diving beetle vs water scavenger beetle vs whirligig beetle

Three kinds of water beetle you might spot in the same pond, and how to tell them apart.

| | Diving beetle | Water scavenger beetle | Whirligig beetle |
|---|---|---|---|
| Family [2][31][24] | Dytiscidae | Hydrophilidae | Gyrinidae |
| Antennae [2] | Long and thread-like | Short, ending in a club | Short, ending in a club |
| Where it swims [2][31] | Dives and swims under water | — | Whirls about on the water surface |
| Eyes [31] | Not split | Not split | Each eye split into an upper half for air and a lower half for water |
| Underside [2] | No keel between the legs | Many have a keel-like ridge between the legs | — |
| Swimming legs [8] | Hind legs row together like oars | — | — |

A dash means we did not find a source we trust for that cell.

### Are diving beetles endangered?

Most diving beetles have never been assessed, and many are common. But some of the biggest are rare and protected, and one may already be extinct.

- **IUCN Red List:** Varies by species (Trend unknown). Europe’s biggest diving beetle, Dytiscus latissimus, is Vulnerable on the IUCN Red List and has declined fast since the 1960s. [32][25][33]
- IUCN Red List, species by species
- **Threat: Drained and polluted wetlands**: Draining lakes and farmland, and fertilisers and pesticides washing into the water, are thought to be behind the decline of Dytiscus latissimus. [25]
- **Threat: Towns and climate change**: Urban growth, deforestation, climate change and alien species are also on the list of suspected causes. [25]
- **Threat: Fish in ponds**: Fish are one of the main limits on where diving beetles live: they eat the larvae and compete for food. [2][34]
- **Threat: Over-collecting**: In Japan, Dytiscus sharpi became one of the country’s most critically endangered insects through over-collecting and habitat loss. [35]
- **Helping: Protected by law** (Annex II): Dytiscus latissimus and Graphoderus bilineatus are the two diving beetles listed in Annex II of the EU Habitats Directive. D. latissimus is also protected by the Bern Convention. [25][36]
- **Helping: Counting beetles**: Scientists in Germany and Latvia tested trap-and-recapture methods to estimate how many Dytiscus latissimus live in a lake for the first time. [25]
- **Helping: Searching for a lost giant**: Ten forgotten museum specimens gave the first exact locality for Megadytes ducalis in Bahia, Brazil, so scientists can now go and look for it alive. [28]
- **Helping: Wildlife ponds**: Fish-free ponds with plenty of water plants are likely to suit them best, since fish eat the larvae and females lay eggs in plant stems. Diving beetles are also used as indicators of healthy ponds. [2][30][34]
- **Dytiscus latissimus** (VU): Europe’s largest diving beetle, 44 mm long, now rare across its range. [32][25]
- **Graphoderus bilineatus** (VU): The other diving beetle on Annex II of the EU Habitats Directive. [36][25]
- **Megadytes ducalis** (EX): The world’s largest diving beetle, from Brazil, known only from old museum specimens. [29][28]

### Diving beetle signals

- Tail tip touching the surface: Refilling the air store under the wing cases before the next dive. [5][2]
- Bubble at the tail tip: Breathing from the bubble, which also draws a little oxygen from the water. [2][6]
- Sudden backwards dash: An escape move: speed jumps from 0 to 27 cm/s in a twentieth of a second. [8]
- Milky fluid behind the head: The beetle feels threatened and is using its chemical defence. Leave it alone. [17][2]
- Larva hanging head-down from the surface: A water tiger breathing through its tail tube and waiting for something to swim past. [2][20]

### Looks

- **Male great diving beetle**: Glossy dark olive-brown with a yellow rim. Smooth wing cases and round, suction-cup pads on the front feet. (27–35 mm · uses his suction cups to hold on to a female) [1][3]
- **Female great diving beetle**: Same colours as the male, but the wing cases usually have long grooves, and the front feet are plain. (Grooves make her harder to grip. In some species, such as Dytiscus lapponicus, some females are smooth instead.) [3][4][16]
- **Larva (“water tiger”)**: Long and thin, with a flat head, big curved jaws and a breathing tube at the tail tip that it pokes up through the surface. (Up to 60 mm in the great diving beetle, longer than the adult) [1][2][19]
- **Sunburst diving beetle**: Thermonectus marmoratus: shiny black, scattered with bright yellow spots. (Famous for its milky steroid defence and its larvae’s bifocal eyes) [17][11]

### Diving beetle quiz

1. Where does an adult diving beetle keep its air? **Under its wing cases.** The air store sits between the wing cases and the abdomen and is refilled at the surface. [5][2]
2. What is the larva of a diving beetle nicknamed? **Water tiger.** The fierce, long-jawed larvae are called water tigers. [2]
3. How does a big diving beetle like Cybister move its hind legs when swimming? **Both together, like oars.** Both hind legs stroke at the same time. [8]
4. What do males use their special front feet for? **Holding on to a female.** The suction-cup pads grip the female’s back during mating. [3]
5. Why do diving beetles sometimes land on cars? **Shiny dark paint reflects light like water.** Shiny red and black surfaces reflect polarised light like a pond. [10]
6. How does a water tiger eat its food? **Digests it outside its body, then sips it.** Digestive juice goes in through channels in the jaws, then the softened food is sucked out. [19][2]
7. Where do diving beetle eggs usually go? **Inside the stems of water plants.** Females lay their eggs inside plant stems below the surface. [30]
8. Where does a grown water tiger turn into a pupa? **In mud on the bank.** It crawls out of the water and buries itself in mud on land. [2]
9. How long can one dive last, depending on the species? **A few minutes to 24 hours.** Dives last from a few minutes up to 24 hours, and one stream beetle stayed under for over 6 weeks. [5]
10. What is special about the sunburst diving beetle larva’s main eyes? **They have bifocal lenses.** Each main eye has a bifocal lens and two retinas. [11]
11. How long is Europe’s biggest diving beetle, Dytiscus latissimus? **44 mm.** It reaches about 44 mm and is protected in the EU. [25]
12. What should you do if you find a diving beetle? **Watch it in the water.** Big diving beetles can nip, so watch them without handling them. [2]

### Sources (checked 2026-10-16)

1. [Wikipedia contributors. Great diving beetle. English Wikipedia (accessed 2026-10-16)](https://en.wikipedia.org/wiki/Great_diving_beetle)
2. [Wikipedia contributors. Dytiscidae. English Wikipedia (accessed 2026-10-16)](https://en.wikipedia.org/wiki/Dytiscidae)
3. [Bergsten J, Miller KB (2007). Phylogeny of diving beetles reveals a coevolutionary arms race between the sexes. PLoS ONE 2(6): e522](https://doi.org/10.1371/journal.pone.0000522)
4. [Karlsson Green K, Kovalev A, Svensson EI, Gorb SN (2013). Male clasping ability, female polymorphism and sexual conflict: fine-scale elytral morphology as a sexually antagonistic adaptation in female diving beetles. Journal of the Royal Society Interface](https://doi.org/10.1098/rsif.2013.0409)
5. [Kehl S, Dettner K (2009). Surviving submerged: setal tracheal gills for gas exchange in adult rheophilic diving beetles. Journal of Morphology](https://doi.org/10.1002/jmor.10762)
6. [Seymour RS, Matthews PGD (2013). Physical gills in diving insects and spiders: theory and experiment. Journal of Experimental Biology](https://doi.org/10.1242/jeb.070276)
7. [Australian National Botanic Gardens. Family Dytiscidae: predaceous water beetles (Waterbugs for Hire / CPBR)](http://www.anbg.gov.au/cpbr/WfHC/Dytiscidae/index.html)
8. [Qi D, Zhang C, He J, Yue Y, Wang J, Xiao D (2021). Observation and analysis of diving beetle movements while swimming. Scientific Reports](https://doi.org/10.1038/s41598-021-96158-1)
9. [Chen Y, Shih MC, Wu MH, Yang EC, Chi KJ (2014). Underwater attachment using hairs: the functioning of spatula and sucker setae from male diving beetles. Journal of the Royal Society Interface](https://doi.org/10.1098/rsif.2014.0273)
10. [Kriska G, Csabai Z, Boda P, Malik P, Horváth G (2006). Why do red and dark-coloured cars lure aquatic insects? The attraction of water insects to car paintwork explained by reflection-polarization signals. Proceedings of the Royal Society B](https://doi.org/10.1098/rspb.2006.3500)
11. [Stowasser A, Rapaport A, Layne JE, Morgan RC, Buschbeck EK (2010). Biological bifocal lenses with image separation. Current Biology](https://doi.org/10.1016/j.cub.2010.07.012)
12. [Maksimovic S, Layne JE, Buschbeck EK (2011). Spectral sensitivity of the principal eyes of sunburst diving beetle, Thermonectus marmoratus, larvae. Journal of Experimental Biology](https://doi.org/10.1242/jeb.058990)
13. [Qi D, Zhang C, Wu Z, Shen C, Yue Y, Ren L, Yang L (2023). Dynamics and hydrodynamic efficiency of diving beetle while swimming. Heliyon](https://doi.org/10.1016/j.heliyon.2023.e14200)
14. [Jones KK, Cooper SJB, Seymour RS (2019). Cutaneous respiration by diving beetles from underground aquifers of Western Australia (Coleoptera: Dytiscidae). Journal of Experimental Biology](https://doi.org/10.1242/jeb.196659)
15. [Csabai Z, Boda P, Bernáth B, Kriska G, Horváth G (2006). A ‘polarisation sun-dial’ dictates the optimal time of day for dispersal by flying aquatic insects. Freshwater Biology 51: 1341–1350](https://doi.org/10.1111/j.1365-2427.2006.01576.x)
16. [Iversen LL, Svensson EI, Christensen ST, Bergsten J, Sand-Jensen K (2019). Sexual conflict and intrasexual polymorphism promote assortative mating and halt population differentiation. Proceedings of the Royal Society B](https://doi.org/10.1098/rspb.2019.0251)
17. [Meinwald J, Huang Q, Vrkoc J, et al. (1998). Mirasorvone: a masked 20-ketopregnane from the defensive secretion of a diving beetle (Thermonectus marmoratus). PNAS 95(6): 2733](https://doi.org/10.1073/pnas.95.6.2733)
18. [Classen R, Dettner K (1983). Pygidial defensive titer and population structure of Agabus bipustulatus and Agabus paludosus (Coleoptera, Dytiscidae). Journal of Chemical Ecology](https://doi.org/10.1007/BF00988037)
19. [Inoda T, Kamimura S (2015). Choice of prey body parts for effective feeding by predaceous diving beetle larvae, Dytiscus sharpi sharpi. Journal of Insect Behavior](https://doi.org/10.1007/s10905-014-9475-z)
20. [Inoda T (2012). Predaceous diving beetle, Dytiscus sharpi sharpi larvae avoid cannibalism by recognizing prey. Zoological Science](https://doi.org/10.2108/zsj.29.547)
21. [Burton LS, Keenan TA, Rodela TM, Toxopeus J (2026). Overwintering under the ice: seasonal shifts in cold and hypoxia stress physiology of three winter-active pond insects. bioRxiv preprint](https://doi.org/10.64898/2026.08.05.743153)
22. [Inoda T, Tajima F, Taniguchi H, et al. (2007). Temperature-dependent regulation of reproduction in the diving beetle Dytiscus sharpi. Zoological Science](https://doi.org/10.2108/zsj.24.1115)
23. [Kim H, Kim JY, Kim K, et al. (2025). The complete mitogenome of Dytiscus marginalis czerskii. Mitochondrial DNA Part B](https://doi.org/10.1080/23802359.2025.2528577)
24. [Bilton DT, Ribera I, Short AEZ (2019). Water beetles as models in ecology and evolution. Annual Review of Entomology 64](https://doi.org/10.1146/annurev-ento-011118-111829)
25. [Balalaikins M, Schmidt G, Aksjuta K, et al. (2023). The first comprehensive population size estimations for the highly endangered largest diving beetle Dytiscus latissimus in Europe. Scientific Reports](https://doi.org/10.1038/s41598-023-36242-w)
26. [Rashed AA, Aly ES, Mashlawi AM, Bayoumy MH (2025). Density-dependent mortality of the diving beetle, Rhantus elevatus preyed upon Culex pipiens larvae. Journal of Experimental Zoology A](https://doi.org/10.1002/jez.2873)
27. [Onen H, Kaddumukasa MA, Kayondo JK, Akol AM, Tripet F (2024). A review of applications and limitations of using aquatic macroinvertebrate predators for biocontrol of the African malaria mosquito. Parasites & Vectors](https://doi.org/10.1186/s13071-024-06332-3)
28. [Hendrich L, Manuel M, Balke M (2019). The return of the Duke: locality data for Megadytes ducalis Sharp, 1882, the world’s largest diving beetle. Zootaxa](https://doi.org/10.11646/zootaxa.4586.3.8)
29. [Wikidata. Megadytes ducalis (Q1311614): IUCN conservation status Extinct, IUCN taxon ID 12944](https://www.wikidata.org/wiki/Q1311614)
30. [Inoda T (2011). Cracks or holes in the stems of oviposition plants provide the only exit for hatched larvae of diving beetles of the genera Dytiscus and Cybister. Entomologia Experimentalis et Applicata](https://doi.org/10.1111/j.1570-7458.2011.01140.x)
31. [Blagodatski A, Kryuchkov M, Sergeev A, et al. (2014). Under- and over-water halves of Gyrinidae beetle eyes harbor different corneal nanocoatings. Scientific Reports](https://doi.org/10.1038/srep06004)
32. [Wikidata. Dytiscus latissimus (Q906785): IUCN conservation status Vulnerable, IUCN taxon ID 6970](https://www.wikidata.org/wiki/Q906785)
33. [Wikidata. Dytiscidae (Q327149)](https://www.wikidata.org/wiki/Q327149)
34. [Liao W (2024). Water colour shapes diving beetle (Coleoptera: Dytiscidae) assemblages in urban ponds. Insects 15(5): 308](https://doi.org/10.3390/insects15050308)
35. [Nagata N (2019). The complete mitochondrial genome of the critically endangered diving beetle Dytiscus sharpi. Mitochondrial DNA Part B](https://doi.org/10.1080/23802359.2019.1630333)
36. [Wikidata. Graphoderus bilineatus (Q1316227): IUCN conservation status Vulnerable, IUCN taxon ID 9494](https://www.wikidata.org/wiki/Q1316227)

## Measurements & details

- **Wingspan:** 5-80 mm
- **Size:** 0.9-47.5 mm
- **Lifespan:** 365-730 days
- **Leg Count:** 6

## Diet & Feeding

These beetles are fierce hunters, eating many small creatures that live in freshwater!

- **Age differences:** Larvae and adults are both predatory, consuming similar but size-appropriate prey.
- **Primary Foods:** insect larvae, tadpoles, small fish, aquatic worms, snails
- **Foraging Method:** Pursuit

## Ecological connections

- **Hunts:** great pond snail (*Lymnaea stagnalis*) — Adults and larvae prey on these common freshwater snails.
- **Hunts:** common frog (*Rana temporaria*) — Beetles readily consume tadpoles of this widespread frog species.
- **Eaten by:** mallard duck (*Anas platyrhynchos*) — Diving beetles can be a food source for aquatic birds.
- **Hunts:** common house mosquito (*Culex pipiens*) — Diving beetles eat mosquito larvae, but scientists are still testing whether they keep mosquito numbers down.

## Traits

- [Spotted](https://www.snappit.app/explore/traits/spotted): Marked with spots or patches of a different color.
- [Solitary](https://www.snappit.app/explore/traits/solitary): Solitary animals live alone for most of their lives, only interacting with others for mating or parental care.
- [Colorful](https://www.snappit.app/explore/traits/colorful): Colorful describes organisms or objects displaying a wide range of bright and distinct colors.
- [Insectivorous](https://www.snappit.app/explore/traits/insectivorous): This trait identifies organisms whose diet primarily consists of insects and other small invertebrates.
- [Ambush Predator](https://www.snappit.app/explore/traits/ambush-predator): An ambush predator hunts by patiently waiting and concealing itself, then launching a sudden attack when unsuspecting prey comes within range.
- [Wetland](https://www.snappit.app/explore/traits/wetland): This habitat trait identifies species found in wetlands, which are areas of land saturated with water, either permanently or seasonally, including marshes, swamps, and bogs.
- [Carnivorous](https://www.snappit.app/explore/traits/carnivorous): This trait identifies organisms whose diet consists entirely or primarily of animal tissue.
- [Keystone Species](https://www.snappit.app/explore/traits/keystone-species): Describes a species whose presence and role have a disproportionately large effect on its environment.
- [Speedster](https://www.snappit.app/explore/traits/speedster): This trait identifies organisms that exhibit exceptional swiftness in movement for hunting, escape, or travel.
- [Aquatic](https://www.snappit.app/explore/traits/aquatic): Aquatic habitats encompass environments where organisms live predominantly in water, including oceans, rivers, lakes, and wetlands.

## Collections

- [Insects](https://www.snappit.app/explore/collections/insects)

## Safety

**Danger:** 1/5 · Very low

Big diving beetles have strong jaws and can give a sharp nip if picked up, and they ooze a defence fluid when grabbed. Don't touch them: watch from the water's edge, and tell an adult if you get nipped.

## Frequently Asked Questions

### How to identify Predaceous Diving Beetles?

Look for hard wing covers meeting in a line down the back, then compare the antennae, body shape, legs and markings. Metallic colors shift a lot with lighting. Beetle Identifier: upload a photo and compare the visible details.

### What is Predaceous Diving Beetles's wingspan?

5-80 mm

### How big is Predaceous Diving Beetles?

0.9-47.5 mm

### How long does Predaceous Diving Beetles live?

365-730 days

### What does Predaceous Diving Beetles eat?

These beetles are fierce hunters, eating many small creatures that live in freshwater!

### Where is Predaceous Diving Beetles usually found?

Wetlands

### How does Predaceous Diving Beetles hunt?

Pursuit

### How many legs does Predaceous Diving Beetles have?

6

## More Insects

- [Common Eastern Bumble Bee](https://www.snappit.app/explore/common-eastern-bumble-bee) (*Bombus impatiens*)
- [Spotted Lanternfly](https://www.snappit.app/explore/spotted-lanternfly) (*Lycorma delicatula*)
- [Brown-belted Bumble Bee](https://www.snappit.app/explore/brown-belted-bumble-bee) (*Bombus griseocollis*)
- [Eastern Carpenter Bee](https://www.snappit.app/explore/eastern-carpenter-bee) (*Xylocopa virginica*)

---

Source: [Predaceous Diving Beetles: Facts & Places to See — Snappit](https://www.snappit.app/explore/predaceous-diving-beetles)