Invertebrates 101 Chapter 2
The Insects around the Pond - Midges and Mosquitos
We’re following the Worms with the Insects because, most of the time, what look like worms on the rocks of the stream and pond are most often insect larvae. Black Fly larvae, for example, are often mistaken for tiny black leeches, waving in the current. So if we’re going to talk insects, what better place to start than with the much-reviled Mosquito. There’s probably no insect that concerns folks more, what with horror stories about West Nile Virus and Encephalitis, but there’s actually less for pond owners to worry about than you might think, because of the likelihood that females attempting to lay their eggs in a pond are likely to become fish food, along with their eggs and any larvae that might hatch.
By JJ Harrison (jjharrison89@facebook.com) (Own work) [GFDL 1.2 or CC-BY-SA-3.0], via Wikimedia Commons
First, here are some really cool facts about Mosquitos. All mosquitos and midge-like flies world-wide belong to the family Culicidae, but not all are bloodsuckers, and none of them depend on blood to live. In fact, all the biting flies in this group actually use nectar and other sugary liquids for their energy requirements, not blood. Only the females of certain mosquitos bite and drink blood, and the ones that do aren’t feeding for themselves; they need the proteins in the blood for the production of eggs. None of the males of any of the many species have biting mouthparts, nor do any of the males make the characteristic buzzing noise we commonly associate with mosquitos. Only females buzz, to attract males for mating. All mosquitos have amazingly acute sensory organs, including chemical, visual, and heat sensors. The antennae of the males can detect the scent and sound of females over vast distances and the females that do take blood have over two dozen sensors of the 72 in their antennae specifically tuned to detect blood, while other receptors pick up carbon dioxide and various components that we excrete in our sweat. These mamas mean business.
Their life cycle is equally specialized. Females dive into swarms of males to be fertilized, then lay their eggs very carefully, with some slowly and precisely building rafts of eggs, and others repeatedly flying over the water, “dapping” or bobbing up and down to the water surface and dropping their eggs one at a time, as some dragonflies and damselflies do. Still other species deposit their eggs on vegetation just below water level. All of the mosquitos that lay eggs directly in the water expose themselves and their precious cargo to the fish below waiting eagerly for a tasty meal. Fish ponds tend to REDUCE mosquito populations for this precise reason. Some species lay directly on moist soil to avoid predators, where they may hatch right away or survive drying until a future rainy season washes them back into the water. Either way, the fully aquatic larvae attach themselves to the surface microlayer and feed on algae, bacteria and other microbes that collect there, but remain vigilant to threats, and can quickly swim downwards to escape potential predators. Again, this defensive behavior tends to put them right into the waiting jaws of fish and other underwater predators. After a pupa stage in which they stop feeding but continue to be mobile, unlike most other insects, they hatch into adults and swarm to mate again. The cycle takes from a few days to a few weeks, each female laying hundreds of eggs, hence the potential for massive infestations. In the Arctic, where summers are short, mosquitos swarm to the point that each and every caribou in any given herd will lose up to 300ml of blood, about a third of a pint, EVERY DAY during the season.
Luckily for us, our yards are much more hostile environments to mosquitos than the Arctic. A well-designed backyard pond will naturally suppress mosquito populations, since all of a mosquito’s natural enemies - fish, frogs, tadpoles, dragonfly larvae, not to mention bats and birds - live in and around your pond. You will find more mosquitos in the stale, stagnant water in rain gutters on a house than you will in the circulating water of a backyard pond. If it’s still a concern, here are the four most effective ways of reducing or eliminating mosquito populations:
- Source reduction, removing still or stagnant water where mosquito larvae grow. Properly designed and circulated ponds offer very few places for mosquitos to thrive.
- Biocontrol, using natural predators like dragonflies and bacteria like Bacillus thunbergii. “Bt dunks” are non-toxic and specifically target insect larvae.
- Trapping and/or Repellents to kill or drive off adult mosquitos.
- Exclusion, via mosquito netting and window screening
We’re following the Worms with the Insects because, most of the time, what look like worms on the rocks of the stream and pond are most often insect larvae. Black Fly larvae, for example, are often mistaken for tiny black leeches, waving in the current. So if we’re going to talk insects, what better place to start than with the much-reviled Mosquito. There’s probably no insect that concerns folks more, what with horror stories about West Nile Virus and Encephalitis, but there’s actually less for pond owners to worry about than you might think, because of the likelihood that females attempting to lay their eggs in a pond are likely to become fish food, along with their eggs and any larvae that might hatch.
By JJ Harrison (jjharrison89@facebook.com) (Own work) [GFDL 1.2 or CC-BY-SA-3.0], via Wikimedia Commons
First, here are some really cool facts about Mosquitos. All mosquitos and midge-like flies world-wide belong to the family Culicidae, but not all are bloodsuckers, and none of them depend on blood to live. In fact, all the biting flies in this group actually use nectar and other sugary liquids for their energy requirements, not blood. Only the females of certain mosquitos bite and drink blood, and the ones that do aren’t feeding for themselves; they need the proteins in the blood for the production of eggs. None of the males of any of the many species have biting mouthparts, nor do any of the males make the characteristic buzzing noise we commonly associate with mosquitos. Only females buzz, to attract males for mating. All mosquitos have amazingly acute sensory organs, including chemical, visual, and heat sensors. The antennae of the males can detect the scent and sound of females over vast distances and the females that do take blood have over two dozen sensors of the 72 in their antennae specifically tuned to detect blood, while other receptors pick up carbon dioxide and various components that we excrete in our sweat. These mamas mean business.
Their life cycle is equally specialized. Females dive into swarms of males to be fertilized, then lay their eggs very carefully, with some slowly and precisely building rafts of eggs, and others repeatedly flying over the water, “dapping” or bobbing up and down to the water surface and dropping their eggs one at a time, as some dragonflies and damselflies do. Still other species deposit their eggs on vegetation just below water level. All of the mosquitos that lay eggs directly in the water expose themselves and their precious cargo to the fish below waiting eagerly for a tasty meal. Fish ponds tend to REDUCE mosquito populations for this precise reason. Some species lay directly on moist soil to avoid predators, where they may hatch right away or survive drying until a future rainy season washes them back into the water. Either way, the fully aquatic larvae attach themselves to the surface microlayer and feed on algae, bacteria and other microbes that collect there, but remain vigilant to threats, and can quickly swim downwards to escape potential predators. Again, this defensive behavior tends to put them right into the waiting jaws of fish and other underwater predators. After a pupa stage in which they stop feeding but continue to be mobile, unlike most other insects, they hatch into adults and swarm to mate again. The cycle takes from a few days to a few weeks, each female laying hundreds of eggs, hence the potential for massive infestations. In the Arctic, where summers are short, mosquitos swarm to the point that each and every caribou in any given herd will lose up to 300ml of blood, about a third of a pint, EVERY DAY during the season.
Luckily for us, our yards are much more hostile environments to mosquitos than the Arctic. A well-designed backyard pond will naturally suppress mosquito populations, since all of a mosquito’s natural enemies - fish, frogs, tadpoles, dragonfly larvae, not to mention bats and birds - live in and around your pond. You will find more mosquitos in the stale, stagnant water in rain gutters on a house than you will in the circulating water of a backyard pond. If it’s still a concern, here are the four most effective ways of reducing or eliminating mosquito populations:
- Source reduction, removing still or stagnant water where mosquito larvae grow. Properly designed and circulated ponds offer very few places for mosquitos to thrive.
- Biocontrol, using natural predators like dragonflies and bacteria like Bacillus thunbergii. “Bt dunks” are non-toxic and specifically target insect larvae.
- Trapping and/or Repellents to kill or drive off adult mosquitos.
- Exclusion, via mosquito netting and window screening
