Chiasmocleis ventrimaculata

The dotted humming frog (Chiasmocleis ventrimaculata) is a frog that lives in Ecuador, Brazil, Peru, and Bolivia.  Scientists think it might live in Colombia too.  Scientists have seen it between 0 and 400 meters above sea level.  It is famous because tarantula spiders use them to guard their eggs.

Appearance
The adult male frog is 2.0 to 2.3 cm long from nose to rear end and the adult female frog is 2.1 to 2.4 cm long.  The skin on its back and sides is dark green or gray with gold and light blue spots.  Its underside is yellow-white in color with big gray or brown spots.  Its feet are not webbed.  For a frog, it has short hind legs.  For a frog, it has a narrow head and pointed nose.

Home
This frog lives in tropical forests in the Amazon where there is water in the air, but people have also seen it in places where trees have been cut down and in other places where humans have changed the places where the frog could live.  It spends most of its time on land instead of in the water like a swimming frog or up in the trees like a tree frog.  People have found it hiding in the dead leaves on the ground.  It stays still during the day and looks for food at night. This frog lives in the same place with other frogs that came from the same ancient ancestor frog: Chiasmocleis anatipes, Chiasmocleis antenori, Chiasmocleis bassleri, Ctenophryne geayi, and Hamptophryne boliviana.

Reproduction
This frog has many young ones all at once.  Sometimes they do this after heavy rain.  Many male frogs go to a shallow pond, 50 frogs or more.  Then they float on the water and sing together for the females.  Their singing has a hum in it.  The females lay eggs in water that does not flow: ponds but not streams.  One female frog can lay more than 200 eggs at a time.  The eggs are 2 mm across.  The eggs float in groups on top of the water.  The tadpoles are gray in color.

Food

This frog eats ants.  It is specialized to eat ants, which means its body is shaped to be very good at catching ants and not very good at other kinds of food.

Threats

Snakes and large animals without spines can catch and eat this frog.

Tarantulas

Scientists have seen this frog living in the same burrows or holes in trees as tarantula spiders.  For example the tarantula Xenethis immanis.  The spiders could eat the dotted humming frogs and do eat other kinds of frogs, but they do not eat the dotted humming frogs that live with them.

Scientists think the tarantulas use chemicals to tell which frog is which.  They have seen young tarantulas pick up small frogs, touch them with their mouths, and then put them back down without biting them.  Microhylid frogs, like the dotted humming frog, make chemicals in their skin that taste bad.  Scientists think this might be why the frogs and spiders started living together.

The dotted humming frog is so small that large insects and other animals without spines might try to eat it.  Snakes eat this frog too.  But the tarantula can fight or eat these insects.

The dotted humming frog eats ants.  Ants eat tarantula eggs.  Scientists think the tarantula and the spider live together because the spider frightens away animals that would eat the frog and the frog eats the ants that would eat the tarantula's eggs.  Scientists call this relationship mutualism or mutualistic symbiosis.

Other frogs and tarantulas that live far from South America also live together like this.  For example, there are frogs and tarantulas in Sri Lanka that live together this way.  Scientists think this relationship evolved more than once.

Name

The Latin name of this frog means "stains on its belly."

References

Frogs
Animals of South America