Dobsonflies and fishflies
Dobsonflies and fishflies are large-winged insects belonging to the order Megaloptera, primarily found near fast-flowing water in temperate regions across Asia, Africa, and the Americas. They undergo a fascinating life cycle, starting as larvae, also known as crawlers, which live underwater for two to three years before metamorphosing into adult insects. The larvae are characterized by their large heads, multiple gills, and the ability to swim both forward and backward. Upon reaching maturity, male and female dobsonflies and fishflies mate, often attracted to light during the evening from May to early June.
Adult insects have a short lifespan, with males living just a few days and females up to two weeks. They typically do not feed, focusing instead on mating and reproduction, where females lay thousands of eggs on leaves above water. These eggs hatch into larvae that fall into the water, continuing the cycle. Notably, they are sometimes used as bait in fishing due to their habitat and life stage. With their impressive wingspans and unique physical features, such as large mandibles in males, dobsonflies and fishflies are fascinating examples of aquatic insects.
On this Page
Subject Terms
Dobsonflies and fishflies
Dobsonflies and fishflies are large-winged insects that mainly live near fast-flowing water. The young swim in the water for two to three years before they become flying adults that live less than two weeks. These insects are often used as bait in fishing.
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Megaloptera
Family: Corydalidae
Genus: Various (see below)
Species: Various (see below)
Dobsonflies and fishflies belong to the order of insects named Megaloptera, which means large wings. This order contains about 300 species, which include the related snakeflies and the alderflies in the family Sialidae. The dobsonfish and fishflies are in the family Corydalidae. Members of this family live mainly in temperate regions in Asia, Africa, and the American continents.
Dobsonflies and fishflies begin their lives when males and females mate in the evening between May and early June. Quite often they mate near electric lights. These insect species mainly live near fast-flowing bodies of water with stony or muddy bottoms and plenty of vegetation and weeds.
Although they have large wings, adult dobsonflies and fishflies are not strong fliers. Fish eat them since the flies often fall into the water. The flies probably do not eat, but some may eat flowers. The flies spend most of their short time as adults mating. Males live only a few days, and females may live up to two weeks before they die.
After mating, each female lays 2,000 to 3,000 dark brown eggs. She divides her large eggs into several batches and attaches the batches to leaves above the water. Frequently, these leaves are 9 to 15 feet (2 1/2 to 4 1/2 meters) above the water. Special attachments, called egg bursters, on the heads of the larvae, or young, enable them to break from their shells after 10 to 14 days. The newly hatched larvae fall into the water. Each larva has seven or eight pairs of gills and gill chambers along the sides of its body with which it breathes. They can swim forward and backward by wiggling their bodies and paddling their legs. In North America, these larvae are commonly called crawlers and are often used as bait for fishing. They may remain in their larval state for two to three years.
Each dobsonfly and fishfly larva has a large, round head with two antennae and two maxillary palpi, or short hairs near the mouths, for sensing. Members of some species also have large mandibles, or jaws, which often cross in front of their faces. Behind each larva's head is its three-segmented mid-section called a thorax. Attached to this section are a larva's three pairs of legs. The abdomen, or tail section, is behind the thorax and has several ring-like segments with one pair of gills on each segment. Two sensory hairs called cerci are on the tip of each larva's abdomen.
The larvae live on stream bottoms for two to three years and catch other insect larvae, worms, and small mollusks. During this time they grow in size by molting, or shedding, their skins several times. At the end of this time, they crawl ashore and become adults.
As adults, each dobsonfly and fishfly has four large wings and six legs attached to its thorax. The wings may be brown, yellow, or transparent, or clear, and are made from skin-like membranes. The wings have many brown or yellow veins running through them and are often spotted. Most dobsonflies and fishflies are 4 to 5 1/2 inches (100 to 140 millimeters) long and have wingspans of six inches (15 centimeters). The Acanthacorydalis fruhstorferi species of China and Vietnam has the largest wingspan of any aquatic insect at 8 1/2 inches (21 1/2 centimeters). Adults have long, thread-like antennae, two maxillary palpi, and two large compound eyes. Adult males of some species keep their large crossed mandibles which they had as larvae. Since they likely do not eat as adults, these insects use their mandibles to hold females while mating instead of catching prey.
Species include:
Eastern dobsonfly Corydalus cornutus
New Zealand dobsonfly Archichauliodes diversus
Spring fishfly Chauliodes rastricornis
Summer fishfly Chauliodes pectinicornis
Bibliography
"Fishflies." Missouri Department of Conservation, mdc.mo.gov/discover-nature/field-guide/fishflies. Accessed 15 May 2024.
Hall, Donald. "Eastern Dobsonfly, Corydalus Cornutus." Featured Creatures, University of Florida, entnemdept.ufl.edu/creatures/misc/eastern‗dobsonfly.htm. Accessed 15 May 2024.
Vallie, Sarah. "What to Know about Dobsonflies." WebMD, 30 Nov. 2022, www.webmd.com/a-to-z-guides/what-to-know-about-dobsonflies. Accessed 15 May 2024.