Insect Stowaways

Some insect larvae can travel in the guts of migrating birds.

Bugs, guts, and poop are gross on their own. Add them together, and you’ve got what may be the ickiest news story of the year.

Researchers in Spain have found a species of insect larvae that pass through the guts of migrating birds and emerge in the birds’ droppings, unharmed.

A black-tailed godwit could give stowaway insect larvae a lift, especially during migration, in a newly described way for insects to travel.

P. Gil/Vireo

To make this discovery, the scientists had to trudge through a wet salt marsh to dry places where the birds roost. They then had to pick up piles of bird droppings.

Thousands of water birds called black-tailed godwits stop at the marsh in Spain every year as they trek from their northern breeding grounds to their winter homes in Africa. As they rest, they eat. After they eat, they poop.

Scientists have long known that seeds can survive the strong digestive juices of an animal’s stomach. Birds, rodents, and even people eat seeds in one place and plop them out in another. If conditions are just right, the seeds can then take root and grow into new plants. Scientists have also observed snails that hitchhike by sticking to ducks’ feet and eggs of tiny brine shrimp and other water animals that survive in bird guts.

In the godwit droppings, the researchers were amazed to find bright red larvae called bloodworms. These larvae grow up to be mosquito-like insects called midges. It was the first time that anyone had found living larvae hitchhiking inside the body of an animal.

The researchers studied six sets of godwit droppings and found living larvae in three of the sets. In total, they came up with 95 larvae that were still in one piece. Of these, 12 were alive. They hadn’t been harmed at all by the digestive systems of the birds.

The larvae were probably able to survive the trip because birds don’t fully digest their food when they eat a lot. And, when the birds migrate, they tend to gorge themselves frequently. Bloodworms take advantage of this to travel much farther than they could ever get on their own.

Poop, it seems, can take you places.—E. Sohn

Going Deeper:

Milius, Susan. 2005. When worms fly: Insect larvae can survive bird guts. Science News 168(Dec. 10):373-374. Available at http://www.sciencenews.org/articles/20051210/fob6.asp .

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