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Apr. 02, 2012

Beetle Diversity in Costa Rica

by The Bug Chicks

Click to enlarge images

In our earlier post we talked about how Costa Rica is such a biodiversity hotspot. We saw a mind-boggling amount of insect species, and many of them were beetles. During our stay at the Soltis Center, we filmed and photographed ‘round the clock, and in this post, we wanted to give you a taste of the beetle diversity we found there.

A quick and dirty way to tell beetles from other insects: look at their backs! The forewings are hardened into “shells” called elytra, and as a general rule meet in a straight line down the back of the insect. As always, there are some exceptions, but we’ll save that for a later post! Also, look at their mouthparts. Beetles always have chewing, or mandibulate, mouthparts.

Dynastes sp. Hercules Beetle

Beetles in this genus are often called Hercules beetles because some of the larger species can carry over 800 times their body weight. Many males of Dynastes have large horns that protrude from their heads that they use to for defense, and to battle other males for mates. Often in this genus, males and females are easy to tell apart because their body forms are different. This is called sexual dimorphism. Males have large horns, and the females don’t!

The males of this species have one horn that extends from the head and another that extends from the pronotum.

Chrysina sp. Jewel Scarab

Believe it or not, these beetles are in the same family, Scarabaeidae, as the Hercules beetle! These insects are called “jewel scarabs” for a reason. There are about 100 species in the genus Chrysina and these beetles can be brightly colored, have metallic accents, or have totally metallic bodies. You might think that these guys would stand out from their surroundings, but they’re very well camouflaged, resembling how sunlight shimmers on wet leaves. This effect is due to the many layers of chitin in their exoskeletons refracting light differently through each layer. This gives the beetle its metallic sheen.

To learn more about how the jewel scarab blends in with its environment, you can read the article on Science Daily!

These beetles are prized by insect collectors for their metallic exoskeletons, but we were happy to snap some photos and release it back into the rainforest.

Pyrophorus sp. Luminous Click Beetle

Click beetles are in the family Elateridae. These beetles have a spine that fits into a notch in their mesosterum. They will arch their bodies

Click beetles have a special snapping-latching-jumping mechanism on their undersides. When they arch their backs, a spine from their prothorax gets stuck on a bump on their mesothorax. By exerting pressure on that spine, it slips over the bump, causing the entire animal to pop into the air. That pop is accompanied by a characteristic “click” – hence, their common name.

Click beetles in the genus Pyrophorus have the ability to create light with their bodies. This process is called bioluminescence. These beetles use chemicals in combination with the process of oxidation to create a greenish glow. Pyrophorus beetles are actually considered to be the brightest bioluminescent beetle in the world. When we went out on our night hikes, we could turn off our flashlights and see the lights of these beetles from several meters away!

Even in the light you can see the faint yellow dots on this beetle. But when the lights go out, they glow super bright!

Mallodon sp. Borer Beetle

Ok, we’ll be honest. We’re not 100% sure of the species, but we think it’s in the genus Mallodon (possibly spinibarbus?). We haven’t been able to find much information about this particular species, but another species in this genus (M. dasystomus) bores into the wood of oaks, hackberries, and pecan hickories.

Generally, cerambycid beetles lay their eggs inside dead or living wood of various tree species. Once the eggs hatch, the larvae bore through the wood. Some species will emerge to pupate in the soil, and others will pupate inside the wood and emerge as adults. The adults eat a wide variety of plant materials, including but limited to flowers, leaves and sap.

This cerambycid was the biggest one we’d seen – easily 4 inches long. When we took it out of the plastic container to photograph it, it punctured the plastic with its mandibles! Needless to say, we didn’t handle this one…

We found this huge cerambycid beetle hanging out near our room at the Soltis Center.

Stolas sp. Tortoise beetle

Tortoise beetles are in the family Chrysomelidae, and are pretty easy to distinguish from other species within this family. They have widened elytra that extends beyond their bodies and often completely conceals their legs, giving them the appearance of a very small tortoise. This particular beetle is in the genus Stolas.

The larvae of some species have a cool (and slightly gross) defense mechanism. They will create a “fecal shield” by pulling together a wad of feces and other organic matter and using it to camouflage themselves from natural enemies. We sure wouldn’t eat it (well… Kristie might at LEAST taste it….).

We found this colorful tortoise beetle hanging out on some banana leaves.

 

These are just a few of the beetle species we found around the Soltis Center. With such an incredible amount of biodiversity, we can’t wait to go back and see other species we missed!

About The Bug Chicks

Kristie Reddick and Jessica Honaker are The Bug Chicks. They each have Masters Degrees in Entomology and love to teach people about insects and spiders.

The views expressed are those of the author and are not necessarily those of Science Friday.

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