Mantidfly Spider Parasites - Fake Mantises Mimicking Wasps

If you think this is a mantis, you're wrong. If you think this is a wasp, you're also wrong. This insect is Clemasiella brunia, the wasp-manted fly. It's small-ish, only 3 cm long, wears the colors of a paper wasp, holds itself in the posture of a praying mantis, and is related to neither. It belongs to the order Neuroptera, so its closest relatives are the lacewings, antlions, and owlflies. Its larval biology is one of the strangest things in the insect world, involving a ride on a living wolf spider, a transfer to a second spider, and finally a feast on the spider's eggs. The species ranges from Canada through the U.S. and into Mexico, with records reaching as far south as Nicaragua. Within the genus Clemasiella, about 10 described species are now recognized, but brunia is the only one that occurs north of Mexico. Adult Clemasiella brunia are slim, elongate insects. Their antennae are short and straight, an important character for field identification, because they distinguish this manted fly from many of the wasps it superficially resembles. The wings are perhaps the single most diagnostic character at a quick glance. They are largely transparent, but bear a distinctive thick brown border along the leading edge. Unlike most lacewings, which hold their wings tent-like over the body, C. brunia holds its wings flat over its abdomen, contributing to its wasp-like look. Their body coloration will mislead you because it varies widely. Across the species range, individuals show color polymorphism, with banding patterns in brown, yellow, red-orange, and black, that look like paper wasps of the genus Polistes that live in the same place as the manted fly. In Colorado, a C. brunia may match a yellow and brown Polistes, but in Florida, the same species may appear to be dark red and brown. This is a case of Batesian mimicry, in which a defenseless species evolves the appearance of a dangerous one, and gains protection from predators that have learned to avoid the danger. The Messiella brunia has no sting, no venom, no chemical defenses of any kind, and a body too delicate to inflict any meaningful bite on a predator. Birds, lizards, and other predators that have been stung by paper wasps learn to leave such insects alone, and the manted fly profits from that learned avoidance. The species' resemblance goes beyond appearance and includes behavior. When disturbed, an adult C. brunia will curl its abdomen down and beneath the body, then raise it vertically and pulse it back and forth, mimicking the stinging posture of an aggravated wasp. If pressured further, it flares its wings, leans forward, and continues this sting display. And there are further deceptions. The Messiella brunia is often observed visiting flowers, where it ambushes other flower-visiting insects. C. brunia is frequently seen in aggregations of as many as 20 manted flies in a small area. These aggregations are thought to form in response to male-produced pheromones. The consequence is that an aggregation of manted flies looks like a group of foraging paper wasps. The manted fly resemblance to praying mantises—the rectorial forelegs, the elongated pronotum, the triangular head with wide-set eyes—evolved independently in two unrelated lineages of insect predators. This is an example of convergent evolution. Both the manted flies and the praying mantises are wait-and-ambush predators. They have both been shaped along similar paths despite different evolutionary backgrounds. C. brunia then added a second, more recent layer of convergence—the convergence with paper wasp coloration and shape—on top of the older convergence with mantises. The larval stages of C. brunia are even weirder. Males release a sex pheromone that attracts females. The males approach the female, repeatedly spreads and raises his wings, and simultaneously extends and retracts his rectorial forelegs in a dance. Once the female accepts the male, the pair couples and remains in copulation for up to a whole day. After mating, the male deposits a packet of sperm enclosed in a structured capsule, and the female absorbs it over a period of several days before using its contents to fertilize her eggs. Females can lay over 3,000 eggs, a huge amount to compensate for very high larval mortality. Each larva must locate, hoard, and successfully ride a wolf spider before it has any chance to reach its prey, a wolf spider egg set. Where C. brunia is abundant, it can have a measurable impact on wolf spider populations because each successful larva consumes the entire contents of one spider's egg sac. C. brunia larvae cannot directly penetrate a spider's egg sac, though. They are physically unable to chew their way in. The only avenue to the eggs is to be carried inside by the female spider herself, sealed in with the silk she spins around them. So when a wolf spider passes within reach, the larva grabs the spider's body and clings on. While on the spider, the larva feeds on the spider's blood. This blood feeding sustains the larva for up to several weeks, until the host spider produces an egg sac. But there's a problem. Many of the boarded spiders are males. For a long time, it wasn't clear how a mantid fly larva that had attached itself to a male was able to reach future spider eggs. It turns out that during the mating of wolf spiders, a C. brunia larva on a male transfers across to the female like an STD. When the female spider begins constructing her egg sac, the larva moves from the spider's body onto the eggs and then is enclosed within the silk. Inside the sealed egg sac, it consumes the spider's eggs. Incubation occurs in the same egg sac, and the adult eventually emerges and begins life as a wasp-mimicking, mantis-style ambush predator. Adults perch on vegetation. When a small flying insect comes within reach, the four legs extend forward in a single rapid strike. Adults will also feed on the nectar at the flowers. The combination of ambush predation and floral visitation places Chlemysiella brunia in a small group of insect predators that use flowers as both a feeding station and a hunting ground, a niche shared with the crab spider. The wasp-mantid fly is an insect that wears the costume of one animal, holds the hunting posture of another, parasitizes a third, and is related to none of them. It carries on its body the marks of two distinct episodes of convergent evolution, first with praying mantises, then with paper wasps. Its larvae act as an STD to transfer between two living wolf spiders during mating, and its females lay thousands of eggs because the odds of any of them surviving are almost zero. And its color pattern varies geographically to track whichever paper wasp happens to be the most common locally. 10 out of 10 would recommend Chlemysiella brunia.