Category Archives: Biology

Alternative lawns sign for Mosquito Shield

If you give presentations on the non-target effects of pyrethroid mosquito sprays, here are some modified lawn signs to download and use. I’ve based them on an actual sign from Mosquito Shield, below.

Mosquito Shield lawn sign

First, here’s a sign that simply has an additional part that shows the name and molecular structure one of the two chemicals used by Mosquito Shield (they also use cyfluthrin). It would be nice to have signs like this because it educates neighbors on what is actually in these types of sprays (the companies don’t like to disclose).

Mosquito Shield lawn sign with active ingredient listed

Here’s a mocked-up sign that informs neighbors that the homeowner has also eliminated his/her butterfly and moth problem.

Butterfly Shield lawn sign

Here’s a Firefly Shield sign. It’s really the only beetle people care about and, unfortunately, the numbers of fireflies is plummeting. There are thousands of other beetle species in a typical backyard and none deserves to be dosed with a neurotoxin.

Firefly Shield lawn sign

Spiders are also killed by Mosquito Shield sprays. I suspect many people would see this is a plus but spiders are likely important predators of mosquitoes … and spiders are not hurting humans.

Spider Shield lawn sign

Many bird species depend on insects and spiders to feed themselves and their young, so when you hire Mosquito Shield to nuke your yard you are indirectly reducing the numbers of birds that can survive in an area. I think few homeowners realize this, and Mosquito Shield (and other companies) are unlikely to spell out that consequence.

Bird Shield lawn sign

Finally, pyrethroids get washed into nearby bodies of water and end up killing fish. This might be rare in towns where there is just one person who subscribes to Mosquito Shield … but if everyone in town decided to get sprayed the fish would really take a hit.

Fish Shield lawn sign

More details here.

Identifying mantid egg cases in Pennsylvania

While you are tidying your yard this spring, please be on the lookout for mantid egg cases (oothecae). There are three introduced species where I live in Pennsylvania (Delaware County): the Chinese mantid (Tenodera sinensis), the narrow-winged mantid (Tenodera angustipennis), and the European mantis (Mantis religiosa). We have only one native species: the Carolina mantid (Stagmomantis carolina). Below are photographs of their oothecae.

Chinese mantid (Tenodera sinensis)

Egg case of Chinese mantid (Tenodera sinensis)

Chinese mantid oothecae are typically round (or roundish) roughly textured, and uniform in color.

Narrow-winged mantid (Tenodera angustipennis)

Egg case of narrow-winged mantid (Tenodera angustipennis)

Narrow-winged mantid oothecae are usually rather elongate (in contrast to Chinese mantid and Carolina mantid oothecae). They are also seem to have red streaks, though the color seems to be most noticeable after they age a few months.

Carolina mantid (Stagmomantis carolina)

Egg case of Carolina mantid (Stagmomantis carolina)

Carolina mantids form relatively smooth, teardrop-shaped oothecae with a central portion that is lightly colored. In addition to branches, often found on tree trunks, rocks, and buildings.

Note: Missing from above is a photograph of a European mantis (Mantis religiosa) ootheca, another introduced species that occurs in my area (Delaware County, Pennsylvania). Here’s another pic. They should also be destroyed. Another common name for the European mantis is praying mantis (not preying mantis).

For an excellent overview of all of these species, please see the Cape May Wildlife Guide’s page on mantids.

If you need help identifying an ootheca, I highly recommend posting a photograph on iNaturalist. If you post there, feel free to include my iNaturalist username (@colinpurrington) in your caption so that I can have a look. Not only will you get an answer from the iNaturalist community within a day or two, your submission helps scientists track the spread of invasive species.

What should you do with the non-native oothecae?

Invasive mantids eat butterflies, native bees, honey bees, small birds, and also the native mantid, so when you find egg cases, dispose of them. Here are some suggestions on how to do that:

  • Give them to a neighbor who has chickens
  • Give them to a neighbor who has a pet tarantula, snake, lizard, or fish
  • Put them in a freezer for a week
  • Step on them

But whatever you do, do not just relocate oothecae to some nearby field — that just transfers the problem to someplace where you can’t see the problem. I.e., even though you might pride yourself as being a gentle soul that wouldn’t kill a fly, releasing invasive predators will result, e.g., in monarch butterflies being eaten alive. Don’t be that person. If you simply cannot bring yourself to kill the eggs, ask somebody to help you do the right thing.

But aren’t mantids great for pest control?

Many people (I include myself) grew up being told by highly-educated, seemingly trustworthy adults that mantids are ideal for providing chemical-free pest control in the garden. That view, it turns out, is a myth passed down for generations, and perpetuated by individuals who support themselves by selling egg cases online. Although it’s true that young mantids consume small, pestiferous insects, when mantids are fully grown they tend to camp out on flowers and wait for large butterflies (and birds). I.e., when a mantid is fully grown it will not even look at an aphid. If you really want an insect that eats pests, go buy some ladybugs or lacewings. Mantids are, of course, excellent for controlling butterflies and hummingbirds, just in case you happen to hate those animals.

Some people even believe that mantids can control ticks. They don’t. They are equally ineffective at controlling mosquitoes.

Mosquito traps that work

Spring is officially here so I’ve deployed my collection of mosquito traps (photographs below). In case you haven’t seen them before, each is filled with water and decomposing plant matter (hay and compressed rabbit food), then equipped with special lids (and sticky cards) that prevent females from escaping once they get inside. In addition, eggs that the female might lay are also prevented from developing. All of this happens passively, 24/7, all summer long, without the use of chemicals. I have two from BioCare (~$30 from Gardeners Supply), two from Biogents (~$24 from BioQuip), and one that I made last year (~ $5 in supplies).

Every homeowner should have them. Coupled with other preventative measures (eliminating stagnant water, reducing excess vegetation, etc.), you can knock back mosquito levels and enjoy your yard again. Five units is probably sufficient for an average yard but I plan on making a few more this summer just to make sure.

Ideally, everyone on your block should have them, too, so if you are planning on ordering some you should first send a note to all your neighbors to see whether you can make a bulk order. E.g., if you order a lot of Biogents you can shave a few dollars off of each unit. Buying a bunch might seem like a lot of money but compare it to the cost (~$700) of having a company like Mosquito Squad spray your yard with pyrethroids every several weeks (every year). Using these passive traps also saves all the pollinators that are killed by those pesticides.