Acilius sulcatus is a species of water beetle in the family Dytiscidae. It is fairly large (14.4 – 18.2 mm), with color variation shown throughout its range. Typically it is yellow and black.
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withColor varies throughout the range of A. sulcatus and is not a good identifying characteristic; however, A. sulcatus shows many unique structural morphologies useful for identification. A. sulcatus is easily recognized by its large, distinctive hind legs. The hind legs are long and fringed with setae, forming a paddle-like shape when spread. The body is always wider than the height of the insect, and is streamlined (no spines or other chitinous structures protruding). As in all Dytiscidae beetles, the sternal keel is absent. A. sulcatus is clumsy on land, but it is well adapted for an aquatic lifestyle and is a strong flier. A. sulcatus may also be recognized by its unique reproductive structures. Males have three ventral suction disks used to secure the male to the slippery female during reproduction. Male attachment to females is detrimental to female survival as the mating period may attract predators. To avoid potential death in mating females show modifications of the elytra. The elytra is highly grooved with many suberect setae, making male attachment far more difficult. The male elytra is smooth without setae showing high levels of sexual dimorphism. The competition between the sexes has led to an evolutionary sexual arms race.
A. sulcatus has a worldwide distribution but is found primarily in North Western Europe.
Temporary and permanent water bodies. A. sulcatas shows a generalist response to habitat choice, living in bogs, ponds, streams, etc. As A. sulcatus is able to fly, it is not restricted to a single body of water. A. sulcatus is found in water bodies with high and low levels of vegetation, showing no preference between the two. They dominate in water bodies without any fish predators and are used as a primary indicator of predator presence.
A. sulcatus is a predatory diving beetle which feeds upon small invertebrate and vertebrate prey. Larvae prefer micro-invertebrate prey, such as Daphnia, whereas adults select size-appropriate prey. Known for its high aquatic speed, A. sulcatus actively pursues prey rather than using a sit-and wait ambush strategy seen in other arthropods. A. sulcatus is active both day and night. A. sulcatus larvae capture prey headfirst with their mandibles before injecting digestive enzymes for extra oral digestion. Adults do not use extra oral digestion, instead using their strong mouth parts to devour prey.
A. sulcatus is univoltine, with adults overwintering in deep permanent water bodies that neither dry out nor freeze completely. Mating pairs are found in both the spring and autumn. Females lay their eggs near water on the underside of plant matter. Eggs hatch after about one week. Larval development takes about 30 days, and pupal development takes another 16–28 days.
