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GREAT DIVING BEETLES

DYTISCIDAE: DYTISCINAE

DYTISCIDAE: DYTISCINAE

subfamily

Dytiscinae

known species

380–400

distribution

Worldwide except Antarctica. Large species

are common in northern climates as well as

in the tropics

habitat

Fresh water, including ponds, lakes, rivers,

and some brackish areas near the coast. Can

be found in very small, recently formed pools

size

10–45 mm

diet

Carnivorous. Adults and larvae feed

on aquatic arthropods, worms, fish,

and amphibians. Can be a minor pest

in fish or shrimp farms

lthough comprising only 10 percent of the

species of diving beetles, the subfamily

Dytiscinae, known as the great diving beetles,

includes some of the largest and most conspicuous

of all aquatic beetles. The biggest species, at almost

2 in (5 cm), is Megadytes ducalis; until recently it was

known from only a single specimen apparently

found in a water-filled canoe along the Amazon

River in the late 1800s, and kept at the Natural

History Museum in London.

All Dytiscinae are rapacious hunters as adults

and larvae. The large, yellowish-brown, striped

larvae, called “water tigers,” have hollow, sickle-

shaped mandibles that are used to liquify their prey

with enzymes before sucking up its juices, and they

often attack larger animals, even fish. On reaching

full size, larvae crawl out of the water and pupate in

a hole in the ground, the fresh adult either returning

to the pond or dispersing in search of new water

bodies. Dispersing adults fly powerfully at night, and

may be attracted to lights, or drop down onto shining

objects such as cars or glasshouses, mistaking the

reflected moonlight for a water surface. They have

even been found at oases deep in the Sahara Desert.

left | Dytiscus marginalis The voracious larvae

of this European great diving beetle often eat

vertebrates such as fish, newts, and tadpoles.

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