Sunday, November 27, 2022

Blister Beetle!

A few weeks ago, before it got cold, this inch-long beetle crossed my path. It will probably be the last flashy outdoor insect of the year. It's a sensational one -- a blister beetle in the genus Meloe. Click to enlarge.

It's also called an oil beetle. They are famous for producing a defensive yellow oil from their joints when threatened. The oil contains cantharadin, which causes blistering on human skin. 

 It's also famous having a first larval stage that is radically different from its subsequent grub style larval stages. It's called a triangulan. It's tiny, kind of looks like a silverfish, and has three claws on each of its legs from which it gets the name. It's built to travel to a food source. It's only job is to hitchhike on a bee. 

Each species of Meloe beetle preys on a specific kind of ground-dwelling solitary bee. The kind of bee that makes a little nest in the ground, provisions it with pollen, and leaves eggs there to eat and grow. If the blister beetles have their way, those well planned bee babies either end up sharing their food supply or being eaten. 

Meloe triangulans can work together to do something remarkable to get to those bees. They aggregate on a plant and produce chemicals that mimic female bee pheremones. A unwitting amorous male bee attracted to the scent ends up at a ball of tiny insects that latch onto him. When he finds a real female bee to mate with some of the triagulans are transferred to her and get taken back to her nest where they drop off and start pillaging. 

What an amazing product of insect evolution crossed my path that day! 

If you see one of these -- big, dark, long body, short wing covers -- don't touch! 

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