Author Archives: avn2

If you have ever been biking or walking outside during the summer in Texas, then you probably have experienced running into what appears to be “clouds” or groups of tiny gnats. Unexpectedly, you get them all in your mouth, hair, nose and eyes, and no matter what amount of coughing, swatting, or waving of the arms you do, a few blocks later you receive another face-full of gnats. At least that is what occurred to me for the past month. On my way to school each morning I would run into on average 3 clouds of gnats a day. Why they seemed to gravitate towards people’s heads, and why there were so many of them in the same location everyday, I did not know. It wasn’t until I went on my first insect biology field trip that I learned more about them.

Earlier this month, Dr. Solomon’s Insect Biology lab went to Spring Creek Greenway to collect and study insects. One of the first observations I made at the site was a very large cloud of tiny flies. This cloud of insects was much larger than those in the city, and amazingly, they moved in unison. Dr. Solomon informed our class that these insects were most likely “eye gnats” of the order Diptera and genus Liohippelates; and the clouds they formed were called leks.

Liophippelates photo credit: wikipedia.org

Male eye gnats, which are about 1/16^th to 1/8^th of an inch in size, gather together in large groups to attract female mates. Because they are so small, finding a mate on their own would be difficult. In order to further increase their visibility, these gnats often hover over tall objects, which is called “hilltopping”.  In leks the males impress females by rapidly flying in perfect formation. On the down side, these leks make easy targets for predators. This is why oftentimes at the park I noticed dragonflies flying through and around these leks taking bites from the group.

Eye gnats are true flies; they have only two wings and two halteres. Their halteres support them in making quick turns and stops while flying in unison. There can be hundreds and even thousands of eye gnats in one lek. One reason for their large numbers is due to their fast generation times. Eye gnat eggs hatch within 2 weeks and become sexually mature in about 3 weeks. These gnats undergo holometabolous metamorphosis. Eggs are laid in shallow layers of soil or and once they hatch, the larvae feed on decayed plant matter. Eye gnats get their name from the fact that as adults, they drink the moisture from animals’ eyes and sweat. This also explains why they gather around people’s heads. Although eye gnats are mostly harmless, one species, Lioppelates flavipes, is known to transmit pink eye through a bacteria they carry inside of their bodies.  Other species can transmit yaws, a skin disease common in South America.

Eye gnats are interesting flies that are greater together in number. The next time I find my head in a cloud of gnats I will remember that the little guys are only trying to find a mate.

This summer I worked in the greenhouses on Rice University’s campus tending to tallow trees, clover, and other plants. Several different organisms invaded the plants, including spiders and snails. The worst of these pests however, were the spider mites.

While watering the plants, I began to notice that many of the clover and tallow tree leaves were fading to a pale yellow, and everywhere I saw yellow leaves there was always what looked like an orange powdery substance on the plant. In taking a closer look I realized that the “powder” was made up of thousands of tiny orange arthropods, the spider mites.

Spider Mites are not actually spiders but they are mites in the order Acari and family Tetranychidae.  They get the name “spider” from their ability to spin silk webs around the leaves of various plants. There are over 1000 species of spider mites alone, and I think the species I saw was Tetranychus urticae, the red spider mite. Although spider mites do not live longer than a couple of days, their numbers can grow exponentially. One female spider mite can lay 20 eggs a day, and each egg matures into an adult in less than a week. This leads to huge colonies like the one seen in the photo of the clover. The mites eat individual cells on the leaves lowering a plant’s ability to photosynthesize and causing the plant to loose coloration. Pesticides and other treatments are usually ineffective against spider mites because of their fast generation times. Each new generation of these insects develops in 5 to 7 days, which means that a single population of spider mites can build resistance to such chemicals in a matter of weeks.

My professor and lab manager Dr. Siemann suggested that we order ladybugs to rid the greenhouse of these pests. Yes, it is possible to order live ladybugs from the Internet! Ladybugs also known as Ladybirds and Ladybeetles are in the beetle order Coleoptera and family Coccinellidae. These insects are amazing predators against pests such as aphids and mites that attack crops and other plants. They are actually considered sacred in many areas of the world because of the “good luck” they bring to farmers. There are over 6000 species of ladybugs; the most common species of ladybug found in the U.S. and the one we used in the greenhouses is Coccinella septempunctata. This ladybug has red elytra with black spots. Other species of ladybugs are black, orange, yellow, and even blue. Ladybugs possess the ability to secrete smelly and disgusting substances when in danger. In what is called aposematic coloration, their colorful elytra ward off predators by letting them know they taste bad! Like all beetles, ladybugs have powerful mandibles, which are sharp teeth-like structures that move horizontally. These allow them to munch on several tiny organisms.

Once our package of 4000 ladybugs arrived from California we went through the process of distributing them on the leaves of each plant. This took some time, as ladybugs are quick to fly! Surprisingly, over the next week the number of spider mites decreased substantially as well as the number of other pests. The ladybugs must have had a huge appetite from their trip to Texas!

Watch this video of ladybugs eating aphids!