This gorgeous female Cicindela splendida emerged recently from one of my rearing containers. She was one of several 3rd instar larvae that I collected this past June from their burrows in a dolomite glade in southeastern Missouri. I had suspected they might represent this species because of the bright, metallic sheen on their heads and decided to rear them out to find out for sure. Rearing tiger beetles is fun and easy—all you have to do is fill a container with native soil, make a “starter” burrow¹ and drop them in. In this case, I also partially sunk a native rock into the soil in the center of the container, something I have started doing recently as it gives the emerged adult an elevated and more visually appealing surface on which to perch than the soil should I desire to take photographs.
¹ Larvae will dig new burrows on their own, but starter burrows allow you to place the burrow where you want it. They are essential if more than one larva is introduced to the container, as wandering larvae will fight when they encounter each other. I like to start the burrow in a corner of the container (a pencil works great for this) and push down to the bottom of the container so I can see into the burrow from outside to monitor the larva as it develops. After introducing the larva to its burrow, I push the soil around the entrance to seal it lightly to keep the larva from immediately crawling back out. The larva will eventually reopen the burrow but generally accepts it, digging it out further to its liking and shaping the entrance to precisely fit the size and shape of its head.
With tiger beetle rearing, feeding time is fun time! Our lab rears insects for testing in abundance, and there are always leftovers. Really just about any insect that can be pulled into the burrow will be acceptable as prey, but lepidopteran caterpillars are my favorite. I use mostly early instar tobacco hornworm larvae, choosing the size as appropriate for the size of the tiger beetle larva—the big ones (e.g. 3rd instar Tetracha) can handle caterpillars 35-40 mm in length and 6-8 mm in diameter, while neonates must be used for the smallest ones (e.g. 1st instar Cylindera celeripes and C. cursitans). I find it endlessly entertaining to sneak up on the larva sitting at the entrance of its burrow, slowly position a caterpillar above the burrow entrance with forceps, and dangle it to entice the tiger beetle larva to lurch out, grab the caterpillar, and drag it down into its burrow—all in a split second! If the larva drops down from the burrow entrance during my approach I just drop the caterpillar into the burrow (though this isn’t nearly as much fun).
Copyright © Ted C. MacRae 2011