#marsh fly

One of fourteen species, all endemic to New Zealand, from the Sciomyzidae family, also known marsh flies or snail-killing flies.

Sciomyzids are found in most parts of the world, but are uncommon in Australasia and Oceania. They're common along the edges of ponds and rivers, and in marshy areas, where the adults drink dew and nectar and the larvae give molluscs screaming nightmares. The maggots are predators or parasites or both of snails, slugs, snail eggs, and freshwater Sphaeriid Fingernail Clams. Many of the species have semi-aquatic or fully aquatic larvae.

Neolimnia castanea presumably preys on terrestrial snails in the wild, given where the adults are found, but also readily attacks aquatic snails in the lab.

Marsh Fly - Sepedon sp.

Continuing on from last week’s post, today we have more posts that showcase insect photography through the Pixel 4. While this insect isn’t particularly significant, I’m pretty sure this was the first new insect specimen captured with this phone. As nature returns back to the flow of Spring and the front yard reawakens, the first insects to emerge are usually the Flies. There’s plenty of decaying matter to enjoy after a winter thaw, and this is where Flies thrive (the eggs are likely to have overwintered, hatched and developed, or pupae overwintered depending on the specie). The front yard houses plenty of leaf litter that isn’t able to be cleaned, and thus, the Flies find a paradise to enjoy. However, this type of Fly operates with a different strategy. Not to be confused with March Flies - Bibionidae, this specimen is a Marsh Fly (no common name) - of the family Sciomyzidae. With the wings being folded on top of each other and resting behind the thorax, along with the body shape, I thought this might have been a Soldier Fly, but research pointed somewhere else.

This new family of Fly can be easily distinguished from the others by looking for their very prominent antennae. Most of these Marsh Flies also have wings with markings on them, usually spots from other images I’ve seen. As the family name suggests, these Flies are expected to be found near water sources; these Flies need water for their offspring. In contrast to other maggots who eat decaying matter and leaf litter, these larvae are predatory in this family and especially in this genus. Some larvae parasitize their prey while others fed on them. In this case, snails are the prey item! Such a reputation for the consumption of snails has given Marsh Flies the nickname, “Snail Killer Flies”. Adults, however, are much more placid and feed on nectar and juices, making approaching them a task to be done without fear.