Author: Lindsay Patterson / Source: Atlas Obscura

Rosemary Malfi first encountered conopids while she was dissecting bees, early in her graduate career.
She was looking for the type of parasite you can only see with a microscope. But it was difficult to look past the parasites that filled the bee’s entire abdomen.The parasitic conopid fly is the Mafioso of the bumblebee world: It forces bees to dig their own graves. The saga begins when a worker bee innocently approaches a flower where an adult, female conopid fly lies in wait. After identifying its target, the fly dive-bombs the bee in mid-air, tackling it to the ground. The bee is stunned, but quickly reorients itself and flies off. Nothing seems wrong, but it’s been implanted with an egg, which will soon hatch and eat its body from the inside.
The egg’s new home is the bee’s fat stores. What was meant to be a source of energy for the bee becomes a source of nutrition for the fly larva. After devouring the fat stores, the growing larva continues to hollow out the bee’s body. It consumes internal tissues as if clearing furniture from someone’s apartment. The bee’s body is both the fly’s food and its home.
This micro-nightmare remains private for around 10 days, until the bee succumbs to its fate. It lands on the ground and digs itself into the soil. In a zombie-like motion, it uses its little bee legs to tunnel into its own grave, and die.

But the fly is very much alive, hibernating inside the closed coffin of the bee’s body. In the spring, the adult fly squirms out of the bee’s carcass like it’s shedding a false skin, ready to begin the cycle again.
This is not a singular nightmare for an unlucky specimen. Malfi’s collection of dissected bees had been gathered from 12 different sites, and each group was beset by conopids. “We were surprised by just how many of them there were,” she says. “A third of the bees had parasitoid fly larvae living inside of them.” Malfi isn’t sure how exactly the larvae force bees to dig their own graves. But she speculates that the fly somehow flips a switch in the worker bee’s brain to make it act like a queen bee preparing to hibernate for the winter.
Malfi, a postdoctoral scholar at the University of California-Davis, is now a leading expert on the relationship between conopids and bumble bees. “Conopid flies are fascinating, and we don’t have a great grasp of how natural enemies influence [bumble bee] populations generally,” she says.
Now is a critical time to figure it out, because many wild bumble bee species are at risk. Among the most threatened species, scientists have documented sharp population declines….
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