Aquatica leii

Aquatica leii, also known as Lei's swamp flasher,is a species of firefly that is native to mainland China.^[1] It is one of nine species of aquatic fireflies, seven of which belong to the genus Aquatica, within the subfamily Luciolinae.^[2] The members of this genus are named for their aquatic larval stage. They have been listed as a protected species in China since June 2023.^[3] Their declining numbers are thought to be largely due to their sensitivity to water quality and pollution.^[4]

As larvae, A. leii are black in color with soft bodies and yellow spots.^[5] These larvae have tracheal gills and spiracles, as well as 10 pairs of eversible organs.^[6] These organs are white, forked, defensive glands that emit a "strong pine smell" when they are disturbed, most likely for defense.^[7] A. leii larvae also possess "flower-shaped" protrusions that have multiple spines on them.^[6] Adult members of this species are approximately 6.5-11mm in length and have a pale yellowish orange pronotum with a brown rim.^[5] Females are generally larger than males.^[8] Males and females produce a yellowish-greenish light as larvae and adults.^[9]

First mentioned under the genus Luciola in X. Fu et al's 2006 publication of The Canadian Entomologist, it was reclassified under the genus Aquatica in 2010.^[1]

Aquatica leii can be found in the province of Hubei in Mainland China. As larvae, they live in shallow fresh water sources such as streams, rivers, ditches, and rice fields.^[1] Larvae are unable to swim and exist as bottom dwellers, attaching themselves to substrate or hiding under sand.^[1] These larvae have the ability to glow spontaneously from light emitting organ(s) on the second to last segment of their abdomen.^[1] It is thought that this is a form of aposematism and that as adults, this ability becomes a sexual signal to aid in finding a mate.^[7] As adults both males and females retain this ability to flash from their light emitting organ, with males flying at dusk in search of females.^[10] Once a female is located, the male switches to a new "courting pattern", and the female flashes a pattern in response.^[10] Males may attempt to court the same female and it is thought that sexual selection may be based on the bases of the male flashes.^[10] After mating, females lay their eggs on the leaves and stems of aquatic plants above the water line and then die after approximately 7 days.^[10] The adult stage typically lasts around a total of 10 days for this species.^[10] The larval stage has been known to last approximately two years.^[10] When larvae reach maturity, they emerge onto land and form a "pupal cell" using soil. They remain in this cell for around 5 days before emerging as adults.^[10] Emergence occurs between the months of April and September.^[10]

Aquatica leii exhibits predatory behavior and specializes on a diet of aquatic snails.^[10] Larvae typically search for food at night, and more than one individual can be seen feeding on the same snail.^[11]

No species has been witnessed preying upon A.leii, but they have been witnessed becoming captured in a spider's web, with their flashes attracting other members of their species to the web as well.^[10] Due to their aquatic larval stage, they face multiple threats including, but not limited to: habitat loss (water bodies drying), water pollution, and overall declines in water quality.^[12]

Due to their diet of freshwater snails, it has been suggested that A. leii may be of use as a biological agent, potentially able to control the spread of parasites like liver flukes, which utilize these snails as an intermediate host and can cause schistosomiasis.^[1]