Mosquitoes Part II: Larval Breeder

Ask someone where to find mosquitoes and they’ll likely answer with some clever little quip. “On my patio” or “wherever I hang my hammock” they might reply, doubtless referring to the bites of adult female mosquitoes out for a blood meal. When asked where to find mosquitoes larvae these same comedians may be stumped. Finding mosquito larvae in areas where they are endemic is surprisingly simple, just find the water.

Look for standing swatter, without fish, even tiny ones. Don’t think just because the garden lacks a pond there aren’t mosquitoes breeding surprisingly close to home. A bloodbath, a puddle beneath the garden spigot, the terracotta base of a potted plant, all may be home to scores of squirming mosquito larvae. Even if it hasn’t rained in weeks one might find that condensation from a window air conditioner has built up in a clogged rain gutter to provide a tiny oasis for breeding mosquitoes.

During their aquatic stage larval mosquitoes eat by filter feeding. They’ll feed on aquatic bacteria, fungi, algae, and nearly anything else that they can strain out of their battery habitat. However clear that water in the dogs bowl in the garden one may rest assured it contains enough microscopic food for the larvae to developers so don’t think it isn’t worth checking. Additionally don’t overlook a potentially rich breeding sight simple because it doesn’t seem as if it could contain enough water. The cup-like bases of numerous plants accumulate water in which a number of mosquito species may breed, and the Asian Tiger mosquito has been introduced to the United States via the scant water held in automobile tires shipped from overseas.

Housing the larvae is really a simple matter. Any wide-mouth clear vessel will do in a pinch, but a special breeding vessel is simple to make and removes the difficulty of capturing adults without them escaping.

Gather the supplies:

  • 2 identical plastic containers with lids.
  • 1 fine mesh screen (just a few cm square)
  • 1 99 cent store plastic funnel
  • Hot glue or silicone caulking
  1. Cut a hole in the bottom of one plastic vessel. Make it as big a hole as you can while still leaving enough flat surface for gluing the screening.
  2. Glue the screening over the hole and set aside. This part will be the top of the breeding chamber.
  3. Cut out the center of the two lids, leaving a small amount (2-4mms, 1/8-3/16in)of flat surface.
  4. Cut the top (inlet) of the funnel so that it is of a size to rest on the rim remaining of the lid.
  5. Cut the bottom (outlet) of the funnel to remove the stem. If the remaining opening is smaller than a flying mosquito, cut it larger (about 1cm, 3/8in).
  6. Place on lid right-side-up on the work area and place the up-side-down funnel upon that. Connect the two using hot glue or contact cement.
  7. Fit the second lid up-side-down over the funnel cone and glue the whole together.

With the whole thing assembled and the glue dry the only thing remaining is to place the collected water and larvae inside and wait.The vessel with the t is the top of the breeder, while the unaltered vessel is the reservoir. When placed in a Northern window (for those in that hemisphere) the microorganisms on which the larvae feed will thrive and in a matter of days develop into adults. The adults will fly up into the cone of the funnel and become stuck in the upper chamber. At this point the upper chamber and cone can be uncoupled from the bottom and briefly frozen to stun the adults for transfer to a suitable killing vessel.

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Large vessel in Northern exposure window.

I like to use containers that have a bit of a recessed lid, the inexpensive plastic food storage canisters sold at most grocery stores work great. With those sorts of lids it’s important to fill in the area where the funnel passes through the second lid so that there is no area in which adults may become stuck. This sort of breeding vessel is suitable for many aquatic dipterans. In the case of mosquitoes it could be a good idea to first paint the top half (when assembled) of the vented vessel black. A number of mosquitoes are known to be attracted to black preferentially and it can serve to speed their transition through the funnel trap into the top vessel. If a large number of breeders are going to be assembled it could be a good idea to purchase a large roll of fine, stiff, mesh. Using the mesh one can form a significant number of funnel traps at exceedingly little expense.

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Mosquitoes Part I: The Zika Vector

For residents of the United States it’s been hard to ignore the alarmist “news” about the Zika virus this spring and summer. Like a number of tropical diseases it’s mosquito borne and the particular vector is Aedes aegypti.

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Zika? No! This is a male and it’s the wrong species!

Individuals in northern areas may feel somewhat reassured by the fact that vector insect population data from the Centers for Disease Control shows only a scant few places where A. aegypti have become established. Well… that information is out of date at best and flat out wrong at worst. After all, this is the yellow fever mosquito we’re dealing with. Remember yellow fever, they used to all it the American plague, no one should be surprised that this particular mosquito is all over the place in North America.

Want some specific location data? I’ve been sampling populations in my area (at two locations one 30 miles East of Rochester, NY, the other a further 10 miles East of that) for a few years now just for fun. Wonder of wonder, there’s several species around, including A. ageypti. What’s better than my word? Your own hard data, lest we give in to the complacency of ignorance lets find out what mosquitoes we have in our own backyards!

I should point out that one doesn’t need a microscope to identify mosquito larvae, nymphs, or adults; but in each stage of development they’re wonderful subjects for the microscopist. Larvae (eggs too if you find them) and nymphs make wonderful live or preserved specimens. Newly killed adults may be examined nicely in temporary mounts. Permanent whole mounts in resinous media are only a little more involved. Unlike with other flying insect species, prepared slides of the mosquito life cycle are widely available, but they’re so simple to do at home anyone who isn’t in a mad rush should really consider it.

Obviously one will first need to get a quantity of mosquitoes. Before rushing outdoors to wait for a hungry little vampire in search of a blood meal to land on an arm (which is an option for the impatient) consider: a feeding mosquito will be female, will probably be damaged during capture, and must be suffered to bite. It’s a great deal simpler to collect mosquitoes with a live trap (for adults) or a turkey-baster (for larvae and nymphs). In fact, anyone with an empty jar can run out and collect hundreds of mosquitoes in an few hours, if they consider the aquatic larvae sufficient; and they are! Those larvae will become adults in short order.

This isn’t a series about how to prepare permanent mounts of the specimens, this is about how to get them, and observe them in temporary mounts. Some other time we’ll get into permanent mounts of mosquitoes for now the goal will be simple and three-fold:

  1. Locate a likely source of mosquito larvae, and collect some.
  2. House those larvae in a vessel in which they may mature through all stages of development.
  3. Sample and observe specimens from that vessel representing each stage.

Hey check it out I can be topical! -K

Freezing Cold and Falling Skies

The natural world is home to a seemingly limitless supply of interest for any microscope owner. Nature might not always supply what your looking for, but there is always something to look at. -K

Faced with a seasonably cold winter and a terrible lack of snowflakes suitable for microscopy, I spent the morning thinking about what I might get out and collect now that wouldn’t be available in a few months when the seasons change. Snow is the obvious perishable commodity, of interest are the things carried by it. In particular areas algae and even pollen will color the snow, much to the wonder of people like the late, mad, Charles Hoy Fort.

A peek out the window showed no colored snows in evidence, only driven white powder made up of tiny balls thanks to the wind and temperatures higher up in the atmosphere. Snow, like rain, has the habit of bringing down things from the heavens; rain drops form around a nucleus of minute particulate matter and carry it to Earth, as does snow. Soot from chimneys, dust, pollen and even pollution are some of the more mundane things that fall with snow (or rain), but there is another passenger that comes from much farther.

Micro-meteors bombard the planet constantly and fall to the ground on their own, or with rain and snow as micrometeorites. In warm weather one can collect water from a downspout and search for bits of extraterrestrial material with a rare earth magnet. Anything sticking to the magnet, of minute size, and bearing a characteristic appearance is a likely micro-meteor. With roofs and gutters the way they are one will only end up with what happened to strike the roof.

Snow affords a unique opportunity to take samples from wherever one would like. This afternoon I went out to the garden with a large plastic storage bag and a 1 liter beaker. I held the bag open and dragged it across an area of new fallen snow about one meter square going down 2 centimeters or so. I didn’t pack the snow down and ended up with a quite full 2.5 gallon zip-lock bag of snow. Choosing a similarly undisturbed area I proceeded to pack snow into the beaker.

Things have been meting for a while now and there appears to have been all manner of things hidden in that clean white snow. When everything has melted I’ll take a close look at just what was hidden away and try a little write up of what was found.