Wednesday, October 25, 2017

Virginia Metallic Tiger Beetle

The Virginia Metallic Tiger Beetle (Tetracha virginica), also goes by the name of Big-headed Tiger Beetle and when you look at these pictures it is easy to see how it earned a name like "big-headed." Their face seems to meld into their thorax with very little definition between the two, this gives the illusion that their face and thorax are all one very large head. They are the largest tiger beetle in this genus, and are found throughout much of  the Eastern United States. While they are considered common they are rarely seen, most likely due to the fact they're almost strictly nocturnal. They are attracted to lights at night and spend the night time hours hunting for insect prey to feed on. During the day they hide out under debris of some kind, usually wood piles or rock piles. They are also known to occasionally congregate in large numbers in cracks or crevices of walls or in dry ground during the day.

You are most likely to encounter them in late summer or early fall, but it is not entirely uncommon to see them anytime between late spring and late fall before the first freeze.

No other tiger beetle looks quite like them, not only are they very large for a tiger beetle, they are a dark metallic green from the tip of their head to the tip of their abdomen. The legs, antennae, and mandibles are tan. Eyes are bulbous and dark.

Like all tiger beetles they are incredibly fast and difficult to get a good look at. Most tiger beetles can fly, but like all tiger beetles in the genus Tetracha they are flightless, or very poor flyers. They seem to rely on their rapid running abilities. They are often found near rivers and lakes. They also occur in suburban areas in lawns, open grassy areas and bare ground. I found the one pictured here alongside the Missouri River in St. Joseph. It was scurrying along the sidewalk right outside where I work.

 As both grubs and adults they feed on various insects. Many tiger beetles in this genus seem able to "hear" or sense the underground activity of insects living in the soil. This ability helps them locate potential prey. Their feeding habits can help biologically control things like June Beetles or Mole Crickets (that may be feeding on your turf) while they are still in the grub stage.

We should consider these beetles beneficial and encourage their presence, even if those large mandibles make them look menacing. They are harmless unless you grab one, then you might earn yourself a nip from those oversized chompers, but leave the beetle alone and it will surely leave you alone.

Sunday, October 15, 2017

Acorn Weevil

Acorn Weevils in the genius Curculio can be deceptively difficult to tell apart as they all look similar and have similar lifecyles. However, I believe this one is Curculio glandium. These tiny weevils measure up to 3/8ths of an inch or somewhere between 4mm and 10mm. They range in color from brown to brownish-gray with a somewhat mottled appearance. The distinctive characteristic is the oversized snout, or rostrum as it is referred to. It is easily twice as long as the body. The antennae are attached to the snout and they have large "buggy" eyes. They have a muppet-like appearance making them one of the most adorable beetles in the insect World.
 I KNOW, we aren't supposed to use words like adorable, or cute when describing insects (or any animal) as this anthropomorphizes them, but I'm okay with that.

I find them frequently at the white sheet and mercury vapor light that I put out each evening during the summer months. We have a lot of Burr Oak trees near our crop fields and close to an old pond that dried up. I am assuming the large number of acorn weevils are in direct relation to the amount of oak trees we have.

The female will use the modified tooth-like structures at the end of her snout to chew into the acorn (or depending upon species other tree nuts) and have herself a little meal before depositing a single egg inside.

Once the egg is safely planted inside the acorn, it will hatch and feed on the nut meat inside. Sometime in late fall or early winter the acorns begin to fall from the trees and this seems to signal the larva to begin chewing out of the nuts. Maybe it is the sudden jarring of the nut hitting the ground and a good sound thump to the head that lets them know it is time for the next phase of their development. The tiny white weevil grubs will then burrow into the soil as quickly as they can to avoid any predators that are keeping an eye on the acorns for just such an emerging snack. Once underground they are relatively safe from harm and can finish out their development to the adult form, which can take anywhere from one to as long as five years. I suppose temperature plays a large role in how long this final stage lasts.

The adults will emerge in the spring and mate soon after, and then the cycle will start all over again.
Acorn weevils are found throughout most of the United States and
portions of Canada. 

The feeding habits of these weevils will not cause any damage to fully grown oak trees. However, if there are large infestations of these beetles it may drastically reduce the amount of acorns capable of developing into trees. This will result in fewer trees.

There are two types of acorn weevils, the long-snouted variety in the genus Curculio (Pictured here) and the short-snouted variety in the genus Conotrachelus. The short-snouted variety have a little different lifecycle. Instead of the female chewing into fresh acorns and laying an egg, they will use acorns that have already dropped to the ground and have existing cracks.

If you are a forager and like to collect acorns for human consumption you will have to be quick to gather your harvest. The acorns that have been consumed by weevils will be left untouched by squirrels as they seem to realize there is not enough nut meat to be worth the effort it would take to collect them and bury them. So they go straight for the good nuts that have fallen from the trees and bury them at a record pace. If you find nuts that are lighter in weight and with a single tiny hole those are empty or "bad nuts." It is not uncommon to find some nuts with weevil larva in them, these nuts will often be "moving, or "jumping" like Mexican Jumping Beans as the larva moves around inside them. It is almost as if they are restless to escape their chamber and get on with the next phase of their lifecycle.