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The Pond
by Renee Lara


      Winter and the cold are near, but that does not stop mosquitoes from plaguing us. We can still feel female mosquitoes sucking our blood in order to produce eggs. Male mosquitoes are not the ones that bite and make us itch; they lack the special mouth parts that females use for puncturing the skin of mammals. Instead of making us feel uncomfortable by drinking our blood, they drink nectar from flowers and plants (Oxford 3). Whether they bite us or not, mosquitoes are more noticeable during humid, warm times. Nevertheless, if there is water around, they will be there no matter the season, especially here in Texas. Mosquitoes need water, so the smallest part of the pond in front of parking lot A1, at the Richland campus is a good place for them to develop.

      To build a better understanding of what makes this part of the pond a good place for the mosquitoes' development, I did field research for several days. On September 23, the pond's water had an average temperature of 68 degrees F (20 degrees C). I took the measurements again on September 29. From 3:35 p.m. to 3:57 p.m., the temperature varied from 74 degrees F at the bottom to 81 degrees F near the surface. I noticed that the closer I moved the thermometer to the surface of the water, the warmer it became, as the surface absorbs more of the sun's rays than does the bottom. That is why mosquitoes' eggs are found mostly at the pond's surface. The water in the area at the Richland pond will be used as an incubator for the eggs. The warmer the water is, the sooner the larvae will form and hatch from the eggs. The warmth will help in the developing of the larvae inside the eggs. Eventually the water of the pond will get colder, lengthening the amount of time that will take for the eggs to hatch. In other words, if the pond freezes, the eggs will survive the winter and then be able to hatch whenever the temperature of the pond's water gets higher. With an average temperature of 64 degree F or higher, it will take about two to four days for the eggs to hatch (Ripper 44). This is a perfect environment for mosquitoes to hatch and develop in the section of the pond in front of parking lot A1.

      Female mosquitoes lay their eggs on still water, or where the water current is not too strong (Oxford 4). The current in the pond at Richland is reasonably calm. I figured this out by choosing a starting point at the edge of the pond and a finishing point. The finishing point was a tree which was twenty-seven feet and four inches away from me. Then I threw a flower into the pond and with a stop watch I recorded the time it took to get from the starting point to the tree. The surface current at the point where I was standing is approximately of 4.77 cm/second (1.88 in/sec). By the time the current gets to the part of the pond that is in front of parking lot A1, the pond's current slows and then stops. It stops because the area is saturated with plants, mud, and grass which act like a natural tide breaker. These isolated conditions make this area of the pond a more suitable place for the developing mosquitoes to mature. Having a slow water current or none at all will allow for the mosquito eggs to float on top of the pond's water. The mosquitoes' eggs were much too small for me to distinguish them from other insect's eggs or other wastes, like decayed pieces of plants that were floating around on the water. However, the multitude of bumps covering my arms and legs convinced me that many eggs had been laid in that area of the pond. I was able to find several larvae in the pond, one of which was about one-third of an inch long. Larvae are almost transparent and have small hairs sticking out from their bodies which are used to float. They do not have wings or legs at this stage yet. Larvae need a place with little, or no current (like our section of the pond) in order to be able to hang upside down. They hang upside down because at the end tip of their abdomens, they have a spiracle. The spiracle is a tube-like opening that allows the larva to breathe (Patent 8). If the current is too fast or agitated, the larvae would keep submerging deep into the water; therefore, they would drown due to lack of oxygen. The pond is a perfect habitat for the mosquito larvae because of its calm current.

      While looking over the area of the pond in front of parking lot A1, I was able to notice all the plants, pieces of food, dirt, and dead insects floating around on the surface of the pond. To some of us, that would not be very appetizing, but for mosquito larvae that would be a banquet. All of that matter was brought to that area of the pond by the current. The area of the pond in front of parking lot A1 is about three and a half yards wide, about one twelfth of the pond's largest width (55 yards. 1 ft). The pond's own current pushes the water from the larger area towards the smaller area taking with it plants, insects, and decayed matter. Since the water in the pond absorbs oxygen from the air, there is more oxygen near the surface than at the bottom, thus larvae can mostly be found at the surface of the pond. While hanging upside down in the pond, the larvae can absorb oxygen, water and salts using small hairs (found at the sides of their mouth) called mouth-brushes (Ripper 33). This oxygen absorbency is important for their development. If they did not take in enough oxygen from the surface they would suffocate and die. The larval stage lasts about three weeks, during which they feed from all the microscopic plants, animals and organic matter (Oxford 5) that the Richland pond's area in front of parking lot A1 offers them.

      Throughout this stage, larvae grow and shed their skin about four times (Oxford 5). Those skins will decay in the pond's water and later will be eaten by other mosquitoes' larvae living in the pond's area. After the larval stage they develop into pupae (Patent 12), which I was also able to find in this section of the pond. A pupa is smaller than a larva because the abdomen is curled underneath the pupa's head and its thorax, giving it the shape of a fat comma (Patent 12). The pupa I caught in the pond was only about one-fifth of an inch long. During this stage, they no longer hang upside down, and their air tubes are on the back of the head (Oxford 5). Again, if the current of the pond's area is too fast, they run the same risk of drowning, just as they had when they were larvae. Pupae spend a little less than a week (two to three days) swimming around in the pond taking in oxygen. During this stage all they do is obtain oxygen to breathe from the pond's surface. The pupae do not need to eat throughout this stage (Patent 12); the nutrients they received from the pond's area during their larval stage was sufficient for their development into adult mosquitoes.

      After they finish their pupal stage, mosquitoes are now able to break open their exoskeleton and pull themselves out onto the surface of the water. If there were a strong surface current they would run the risk of being drowned in their attempt to emerge from the pond. The surface current would keep wetting their wings, thorax, and abdomen, forcing them back into the water. Their emerging takes them about ten minutes (Patent 14). If the current in the pond's area were too strong, it would take them longer; increasing the chance that they would drown. That is probably why we can see them standing on top of the water with part of their abdomen inside the pond. They have just become mature mosquitoes and are trying to escape from the surface of the pond.

      When mosquitoes finally emerge and leave the Richland pond, they begin their adult life. Males usually die two to three weeks after mating. Females, however, may last several months and even survive the winter. Mosquitoes usually do not travel more than one mile away from where they were born (Ripper 28, 30). After mating, then, female mosquitoes will more than likely return to the Richland pond's area in front of parking lot A1 to lay their eggs. Then the new eggs will develop in the pond, starting the cycle all over again. Again the good conditions of the Richland pond's area will help more mosquitoes to exist, and it will be like that until the pond is either dried up or removed. Meanwhile, all we can do is wear long sleeves and buy repellent against mosquitoes, so that we will not have to be plagued by them while walking by the pond.


Works Cited
Oxford  Scientific Films.  Mosquito.  New York: G. P. Putnam's sons, 1982.

Patent, Dorothy H.  Mosquitoes.  New York: Holiday House, 1986.

Ripper, Charles L.  Mosquitoes.  New York: William Morrow and Company, 1969.


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