Imagine an insect that seems stitched together from different creatures, possessing the grasping forelegs of a praying mantis, the delicate wings of a lacewing, and sometimes even the striped body of a wasp. These peculiar insects are known as mantidflies.
Mantidflies are not what their name suggests; they are neither flies nor mantises. These intriguing insects belong to the order Neuroptera, placing them in the same group as more familiar insects like lacewings, antlions, and owlflies. They typically measure between 0.5 to 2 inches in length, with a wingspan ranging from 0.2 to 1.2 inches, displaying a variety of colors from browns and greens to yellow, and sometimes red hues.
A defining feature of mantidflies is their elongated prothorax, often described as a “neck,” which supports a triangular head with prominent eyes. Attached to this extended segment are their specialized raptorial forelegs, equipped with spines for capturing prey. These legs fold in a manner strikingly similar to those of a praying mantis, allowing them to ambush small insects. This remarkable resemblance, where two unrelated species evolve similar traits to fill a similar ecological role as ambush predators, is a phenomenon called convergent evolution. Their four membranous wings are typically clear and intricately veined, although some species, like the brown wasp mantidfly (Climaciella brunnea), exhibit patterns and coloration that mimic wasps, providing a form of defense against predators.
A Complex Life Cycle
The life cycle of mantidflies is a complex process known as hypermetamorphosis, involving distinct larval stages. Adult female mantidflies lay numerous tiny eggs, individually attached to short stalks on vegetation. These eggs typically hatch after 11 to 30 days, revealing the first larval stage, known as a planidium.
The planidium is a highly active larva, about 1 millimeter long, characterized by its slender body, well-developed legs, and long antennae. Its primary objective is to find a host, which is most often a spider. Some planidia are “spider-boarders,” actively seeking out a passing spider to attach themselves to, sometimes riding on the spider’s body, even consuming some of its hemolymph. If a larva initially boards a male spider, it can transfer to a female during mating or cannibalization, ensuring it reaches an egg-laying host.
Once a female spider begins to construct her egg sac, the mantidfly larva infiltrates it, often during the sac’s formation. Inside the silk casing, the larva undergoes a grub-like, sedentary form with reduced legs. In this second and subsequent larval stages, it feeds by drawing out the embryonic fluids of the spider eggs using modified piercing-sucking mouthparts. When fully grown, the larva spins a cocoon within the spider’s egg sac and pupates, eventually emerging as a winged adult.
Adult Mantidfly Behavior and Habitat
Adult mantidflies are predatory insects, using their raptorial forelegs to ambush and capture small prey such as aphids, lygus bugs, and other small insects. Their diet also includes nectar, pollen, and tree sap for energy. Some mantidfly species are also cannibalistic.
These insects are typically found in a variety of habitats, including lightly wooded areas with open edges, forests, and fields. They are often observed on vegetation or flowers, where they lie in wait for unsuspecting prey. While some adult mantidflies are active during the day, many species are nocturnal and can be attracted to outdoor lights at night. Mantidflies are widely distributed, with approximately 400 species found worldwide, particularly in tropical and subtropical regions, including North and South America.