Body-snatched zombie ladybugs! It’s not science fiction, but a real invasion of parasitic organisms.

Photograph by Anand Varma; Ecological Parasitology Group, University of California, Santa Barbara

Parasitic Barnacle Heterosaccus californicus
Sheep Crab Loxorhynchus grandis
Welcome to a freakish world where parasites compel their hosts to do their bidding. A male sheep crab infected by a parasitic barnacle is literally feminized. It stops developing fighting claws, and its abdomen widens, providing a “womb” for the barnacle to fill with its brood pouch. Nurtured by the crab, the eggs hatch. Thousands of baby barnacles disperse to infect anew.

Photograph by Anand Varma; Ben Hanelt, University of New Mexico

Horsehair Worm Paragordius varius
House Cricket Acheta domesticus
The house cricket loses its will—and its life—to the horsehair worm. Larvae of the parasite infiltrate the cricket when it scavenges dead insects, then grow inside it. The cricket is terrestrial, but the adult stage of the worm’s life cycle is aquatic. So when the mature worm is ready to emerge, it alters the brain of its host, driving the cricket to abandon the safety of land and take a suicidal leap into the nearest body of water. As the cricket drowns, an adult worm emerges, sometimes a foot in length.

Photograph by Anand Varma; Jacques Brodeur Lab, University of Montreal

Parasitic Wasp Dinocampus coccinellae
Spotted Lady Beetle Coleomegilla maculata
Ladybugs are said to bring good luck—but one infected by the wasp species Dinocampus coccinellae is decidedly unfortunate. When a female wasp stings a ladybug, it leaves behind a single egg. After the egg hatches, the larva begins to eat its host from the inside out. When ready, the parasite emerges and spins a cocoon between the ladybug’s legs. Though its body is now free of the tormentor, the bug remains enslaved, standing over the cocoon and protecting it from potential predators. Some lucky ladybugs actually survive this eerie ordeal.

Photograph by Anand Varma

Spined turban gall wasp Antron douglasii
Valley oak Quercus lobata
When the spined turban gall wasp injects its eggs into oak leaves, it leaves behind something extra: a cocktail of chemicals that induces the plant to build pink structures around the growing wasp larvae, called galls. Safely cocooned, the larvae feed on the plant’s nutrients. How galling.

Photograph by Anand Varma; Linden E. Reid, University of Nebraska Cedar Point Biological Station

Thorny-Headed Worm Pseudocorynosoma constrictum
Amphipod Hyalella azteca
A tiny amphipod, Hyalella azteca, lives in obscurity at the murky bottom of lakes and ponds—unless it’s invaded by the larva of a thorny-headed worm. When the larva matures, the amphipod abandons its safe dark home and swims toward the light of the surface. For the host, it’s a fatal mistake. Waiting above are ducks and other waterfowl keen to eat the amphipods as they surface. But for the parasite—turned orange by pigments pilfered from its victim’s tissue—it’s just part of the plan. Thorny-headed worms can grow to maturity only in the guts of waterfowl.

Photograph by Anand Varma; Pieter Johnson Lab, University of Colorado Boulder

Parasitic Flatworm Ribeiroia ondatrae
American Bullfrog Lithobates catesbeianus
After the flatworm Ribeiroia ondatrae reproduces asexually inside a snail, its larvae find a bullfrog tadpole and burrow their way through its skin, forming cysts around the frog’s developing limbs. With legs added, subtracted, or compromised, the ungainly victim is easy prey for frog-eating birds like herons. Inside the heron, the parasite reproduces sexually. Its eggs reenter the water when the bird defecates, infecting new snails to start another round.

Photograph by Anand Varma; David Hughes Lab, Penn State University

Ophiocordyceps Fungus Ophiocordyceps sp.
Amazonian Ant Dinoponera longipes
Pity the ant afflicted by the mindsucker Ophiocordyceps. When spores of the fungus land on an ant, they penetrate its exoskeleton and enter its brain, compelling the host to leave its normal habitat on the forest floor and scale a nearby tree. Filled to bursting with fungus, the dying ant fastens itself to a leaf or another surface. Fungal stalks burst from the ant’s husk and rain spores onto ants below to begin the process again.

Photograph by Anand Varma; Jeff Harvey Lab, Netherlands Institute of Ecology

White Butterfly Wasp Cotesia glomerata
Cabbage Butterfly Pieris brassicae
Like the spotted ladybug, the caterpillar of the cabbage butterfly plays bodyguard to a parasitic puppet master. A female white butterfly wasp injects a caterpillar with several dozen eggs. The larvae hatch, feed, grow ... then paralyze their still living host and chew their way out. As the caterpillar comes to, the larvae spin little cocoons beneath it. Rather than leave them to fend for themselves, their enslaved host spins an extra silk layer around the cocoons, then stands guard over the brood, flinging its head back and forth to ward off predators.

Photograph by Anand Varma

Nematode Myrmeconema neotropicum
Arboreal ants Cephalotes atratus
Bird droppings gathered by the arboreal ant Cephalotes atratus to feed its larvae sometimes contain a hidden menace: the parasitic nematode Myrmeconema neotropicum. Once inside the ant, the nematode turns its host’s abdomen maroon, so that it mimics a ripe berry attractive to birds. To make its unwitting host even more enticing, the nematode induces the ant to walk with its abdomen raised: Come and eat me!

Photograph by Anand Varma

Parasitoid wasp Hymenoepimecis argyraphaga
Spider Leucauge argyra
The spider Leucauge argyra suffers a series of humiliations at the hands of the parasitic wasp Hymenoepimecis argyraphaga before it is put out of its misery. Paralyzed by the wasp’s sting, the spider stands helpless as its tormentor deposits an egg on its abdomen. Once the egg hatches, the larva holds tight to the spider like some malignant piggybacker, feeding on its internal fluids for a week. When ready to pupate, the larva coerces the spider into setting out on one last, misguided building project. Ripping down its own carefully constructed web, the spider spins a novel one consisting of just a few thick crossing strands. The larva rewards the spider for its efforts by sucking it dry. Then it spins its cocoon at the intersection of the two strands, where it can dangle safely out of reach of predators.