Jingle Bugs: What’s your favourite Christmas beetle?

Spotted flower beetle. (PETR MALEC)

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One of the Christmas traditions of many people is to adorn their Christmas tree with ornaments, which can really bring a lot of additional colour and beauty to the tree. Nature is full of colour and beauty, and in Australia there is a group of beetles called Christmas beetles, which come out around Christmas time. Some of these are black and red, so a hint of Christmas colour. Not sure if anyone has ever used them as a Christmas ornament, but there are many species of beetles that I would contend have the colour that they could even make Charlie Brown’s tree look festive. In this month’s Incredible Creatures we will look at a few beetles that display an amazing array of colours, and could adorn any tree. Which is your favourite?
Jewel Scarabs
Beetles that look like jewelry? There are a couple of different groups of beetles that have “jewel” in the name. There are the jewel beetles (family Buprestidae), also known as metallic wood-boring beetles, which can come in several metallic shades. We have 65 species of jewel beetles in Manitoba.
Although many species have colours worthy of the name jewel beetles, these will not be discussed in any detail in this article; they are worthy of their own article. In this article we will focus on another group of beetles that are natural jewels called the jewel scarabs (genus Chrysina).
The majority of jewel scarabs are bright green, but metallic silver and gold are also common colors, and in some species may be combined with green. Jewel scarabs range from the southwestern edge of the United States as far south as Ecuador. They can be found in pine, juniper, or pine-oak forests, most commonly between 1000-3000m in elevation. There are around 100 species of jewel scarab, and in some places in Central America there may be as many as 15 species in a single location. The jewel scarabs (below) were photographed in Costa Rica while I was assisting in a biodiversity survey in the area.

Jewel Scarabs

The Bright Side of Rotting Logs
Larvae of jewel scarabs live in rotting logs. Many of the nutrients used in larval development come from the bacteria and fungi that decompose the wood.
So even rotting logs have a valuable place in nature, because without them there would be no jewel scarabs. Adults emerge during the rainy season, which for most species is from May to September.
They are active mostly at night, and during the day need to keep from being eaten. Birds are presumed to be the primary predator of jewel scarabs, if they can find them.
When Going Glittery is Good
There are some species of jewel scarabs that are gold (Chrysina aurigana and Chrysina resplendens) and others that are silver (such as Chrysina limbata and Chrysina chrysargyrea). But what benefit is it for a beetle to be coloured like a piece of jewelry? Shouldn’t this make it easier for a potential predator to find them? All of the gold and silver species known are found in evergreen tropical cloud forests.
One hypothesis is that the bright glare from the surface might temporarily blind a potential predator, enabling the beetle to escape. As another possibility, water droplets are everywhere in a tropical rainforest, reflecting light in all kinds of directions.
In this environment a shiny gold or silver beetle may blend in and appear as a flash of light, potentially fooling predators.
For the metallic silver species, another hypothesis is that they are mirroring whatever the beetles are resting on. So when a silver Jewel Scarab is clinging to green leaves, the beetle looks like just another shiny, wet, green spot among the shiny, wet leaves.
Jewel scarabs were used as jewelry by the local people of Central and South America. And they are popular among collectors, sometimes selling for hundreds of dollars each. So they are appreciated and admired by many. Nature’s version of tinsel on trees.
Spotted Flower Beetle
Aside from the jewel scarabs, there are a few other scarab beetles that come naturally adorned in Christmas colours.
There is a genus called Stephanorrhina where species tend to vary from purple to light-green, usually with bright white spots in the forewings.
Some species have brilliant metallic green and red colours, with whitish spots on the forewings.
It’s like they have a scattering of snowflakes on the metallic forewings. It’s hard to imagine an animal more decked out in Christmas colours than that. The species (top right) is the spotted flower beetle, Stephanorrhina guttata. These colourful beetles are found in Cameroon and Nigeria. These cool beetles have been featured on postage stamps from Congo, Burundi, and Gabon.
So enjoy your Christmas festivities and the creative and beautiful ways we decorate our trees, homes and towns. And also take some time to enjoy the beauty that nature provides as well. The golden jewel scarab or spotted flower beetle are not likely on many Christmas wish lists, but seeing some of these colourful creatures would be an incredible experience.
And we are reminded that some things of such humble beginnings, in this case grubs living in rotting logs, can transform into nature’s spectacular jewels.
Incredible Creatures is a monthly contribution to provide information on some of the common yet often not well known creatures that we share space with in Manitoba and abroad.