A Glowrious Beetle

PhengodeslmexicanaCarrieNationPicnicArea13ix14Last weekend I set up my blacklight sheet in the Mt. Wrightson picnic area in Madera Canyon.  It was an opportunity for me to do some blacklighting at a higher elevation (about 5500 feet) than my usual spot at Madera picnic area.

Along with the moths, tree crickets, mantispids, and other insects that were attracted to the light, was one really cool beetle.  It, I should say he, because that’s what it(he) was, was a phengodid beetle, better known as a glowworm.

Relatives of fireflies (Lampyridae) and soldier beetles (Cantharidae), glowworms get their name from the bioluminescence produced by the eggs, larvae, and adult females of the this family.  Males can also be weakly bioluminescent.

There are many other fascinating details in the biology of glowworms.  First, the adults are not known to feed.  The larvae prey on millipedes.  This is a potentially problematic food source for the young, as many millipedes are chemically protected from predators.  Larval glowworms get around this difficulty by coiling around the front of the millipede and reaching under the head of the prey to deliver a dose of toxic saliva through it’s long mandibles.  The saliva contains digestive enzymes that not only instantaneously immobilize the victim, but also begin the process of digestion.  Once the meal is finished, the only reminder of the millipede are the disarticulated rings of it’s exoskeleton!

Wait!  There’s more!  Adult female glowworms are larger than the males and look very much like the larvae.  The main differences are that the adult has compound eyes and mature reproductive organs.  She has no wings and therefore cannot fly.

One of the most striking features of adult males are the large feathery antennae.  These structures function to collect the pheromones released by the female for breeding.

The wings of adult males are short and membranous, giving him a rather unbeetle-like appearance.  Males are often attracted to lights in wooded habitats.

This is a relatively small family of beetles- about 180 species worldwide.  Twenty-three of these are known from North America, representing six genera.  The species that showed up was Phengodes mexicana, based on the dark wingtips.  Another local species, P. arizonensis has uniformly yellowish-brown elytra.

Leave a Reply

You must be logged in to post a comment.

  • Subscribe
  • Categories

  • Archives

  • Recent Comments