Alderflies, Dobsonflies, and Fishflies
01 Jun 2025
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Alderflies, Dobsonflies, and Fishflies
Latin: Megaloptera — Relevance to Fly Fishing:
Megaloptera consists of alderflies, dobsonflies, and fishflies, large insects with aquatic larvae and terrestrial adults.
Where you can find Alderflies, Dobsonflies, and Fishflies
On this map you see where there were observations of Alderflies, Dobsonflies, and Fishflies around the world. This will give you an idea of the global distribution of this class. Note that a class can have many different families, and thousands of species.
Diversity and distribution
The insect class Megaloptera, commonly known as alderflies, dobsonflies, and fishflies, is a small group of insects consisting of around 300 known species. These insects are characterized by their large size, elongated bodies, and membranous wings. Megaloptera is divided into two main families, Corydalidae (dobsonflies and fishflies) and Sialidae (alderflies), with several genera within each family.
Megaloptera insects can be found in various countries across the globe. Their distribution extends across parts of North and South America, Europe, Africa, Asia, and Australia. Megaloptera species typically inhabit environments close to freshwater sources, such as rivers, streams, and ponds.
Life cycles of Megaloptera
The life cycle of Megaloptera insects consists of three stages: egg, larva, and adult. The duration of each stage varies among species and can be influenced by factors such as temperature, humidity, and food availability.
Female Megaloptera lay their eggs near water sources, often on vegetation or rocks. Upon hatching, the aquatic larvae are predatory, feeding on other insects, small fish, and other aquatic organisms. Megaloptera larvae undergo several molts as they grow, and once they reach their final larval stage, they move to the land to pupate. After pupation, the larvae undergo metamorphosis to become adult Megaloptera insects.
Megaloptera and Fly Fishing
Megaloptera insects, particularly their larval stage, are relevant to fly fishing due to their prevalence in aquatic environments and their role as a food source for fish such as trout and bass. Some well-known Megaloptera flies that are targeted by fly fishers include:
Hellgrammite patterns: hellgrammites, the aquatic larvae of dobsonflies, are known for their large size and aggressive nature. Fly fishers can use hellgrammite patterns, typically tied with a segmented body, dark colors, and prominent legs, to imitate these insects. Sometimes a dark, smaller woolly bugger can also imitate this larvae.
Alderfly larva patterns: alderfly larvae are smaller than hellgrammites but can also be a food source for fish. Fly fishers can use alderfly larva patterns with a slim, segmented body and appropriate coloration to match the local larval population, which is mostly a brown color.
In addition to larval patterns, adult Megaloptera flies can be imitated using large, dark-colored dry flies or wet flies that mimic their general shape and appearance. However, adult Megaloptera are less commonly targeted by fish compared to their larval stage.
Flies that mimic species in the insect order Alderflies, Dobsonflies, and Fishflies
There can be thousands of species within an order, and therefore lots of different flies imitating various of these species. Flies can also imitate different stages, for example larvae, pupae and adults.
