Category Archives: Education

Nictitating membrane in a sharpie

If you’ve never been up close to a blinking bird, here’s a GIF that slows down the blink in a sharp-shinned hawk (Accipiter striatus). In addition to using the nictitating membrane to moisten their eye, birds of prey invoke them to protect their eyes from branches during a hunting approach and from prey that might fight back. Humans, sadly, don’t have them anymore, save a little bit of tissue called the plica semilunaris.

As an aside, there’s something rather unnerving about a science fiction movie in which a human is portrayed with functioning membranes. I wonder whether part of our reaction (or my reaction, if it’s just me) is that the membranes might signal the onset of aggressive behavior, where the aggressor is about to strike and wants full protection. I wonder whether animals with functioning nictitating membranes have such a perception. Wouldn’t surprise me.

Sharp-shinned hawk nictitating membrane


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Using mosquitoes’ sweet tooth to control Zika transmission

Now that everyone wants to kill mosquitoes that transmit Zika virus, can somebody please make a transgenic plant that expresses mosquitocidal Bti (Bacillus thuringiensis subsp. israelensis) toxins? Just stick the Bti gene behind a phloem-specific promoter so that the protein gets pumped into the nectar. Then when males and female mosquitoes drink (and almost all do), they die. You could then plant acres of the modified plant nearby towns to protect people from Zika (and anything else transmitted by mosquitoes). The beauty of this method is that you could reduce populations of mosquitoes from an area without spraying, and do so for generations if you modified nectar-producing perennials. I know it’s trendy to dislike GMOs (like vaccines), but I think many people would support them under these circumstances.

And yes, apparently Bti toxins can kill adult mosquitoes (including Aedes aegypti), not just larvae. Klowden and Bulla 1984 demonstrated it, for example. And yes, Aedes aegypti drinks nectar (and probably fruit juice).

Of course, even if somebody had the incentive to make such a plant, it could take a decade to wade through the red tape involved in getting non-regulated status from governments. So if you want to do something today, leave out containers of sugar water (10%) that is laced with Bti (e.g., Mosquito Dunks, which you can buy online or at hardware stores). Maybe add something floral to attract them, too. (A review of olfactory cues suggests that imitation cherry and apple can work. If you don’t have those sitting around, I’d wager a few drops of jasmine flavoring or rose water would work, and those are easily found at local stores.) Even if the Bti doesn’t immediately kill the adult, adults sucking up a big sugar meal can transfer the bacteria to water where they lay eggs, and thus eventually cause the death of any larvae that develop. Note that bees and ants might get interested in your sugar water, but the Bti is completely harmless to them.

And if you don’t want to use Bti, there are plenty of articles on using sugar baits laced with insecticides (e.g., Qualis et al. 2013, Junilla et al. 2015). They really can work: mosquitoes absolutely love sugar and will drink up poisons in the process. These are great if you don’t want to use crop dusters to destroy all insects in the area.

If you have kids and want to entertain them, add food dyes to the sugar bait and then challenge them to find mosquitoes with bellies full of sugar water. For older kids that might be amused by actual science, use two dyes to test attractiveness of two different volatiles (or different sugars). It’s probably rare to recapture one right after a nectar meal, but when distended they reveal gut contents nicely.

Colin Purrington Photography: Insects &emdash; White-footed woods mosquito (Psorophora ferox) nectaring on goldenrod

FYI, the photograph above is a white-footed woods mosquito (Psorophora ferox), not Aedes aegypti. It doesn’t transmit Zika, but illustrates to the unbelieving that mosquitoes drink nectar. 

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Skunk cabbages blooming in the snow

For fans of skunk cabbage (Symplocarpus foetidus), here are a several photographs of from Swarthmore, Pennsylvania. You can see the spadix (an inflorescence) peeking out from inside the warm cavity formed by the spathe (a modified leaf). The spathes are a bit frost damaged because they emerged in early December this year, and their thermogenic capabilities weren’t sufficient to fully weather the cold.

Colin Purrington Photography: Plants &emdash; Eastern skunk cabbages (Symplocarpus foetidus) flowering in snow

Colin Purrington Photography: Plants &emdash; Eastern skunk cabbages (Symplocarpus foetidus) flowering in snow

Here are some that emerged too soon and were damaged by freezing temperatures. There might be fully viable flowers within but I didn’t want to disturb them.

Colin Purrington Photography: Plants &emdash; Eastern skunk cabbages (Symplocarpus foetidus) with frost damage

Finally, here is a photograph from a prior year to show what they look like when they are not damaged by frost. They look like porcelain replicas of rotting beef tongues.

Colin Purrington Photography: Plants &emdash; Eastern skunk cabbages (Symplocarpus foetidus) spathes

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Snow fly

If you’re out on a nature walk today, keep your eyes peeled for snow flies. These are essentially wingless crane flies loaded with antifreeze. This one is a male Chionea scita, I believe. Not much is known about these insects, although there is speculation that at least some members of the genus hang out in rodent burrows eating feces. (Don’t judge.) Please see “The crane fly genus Chionea in North America” (Byers 1983) for more details.

You might note that it has halteres, which is interesting because these are organs used in flight (they are modified wings … which is why flies only have one pair of wings). Would be fun to figure out whether snow fly halteres still work, though that would have to be inferred by anatomy and maybe some electrophysiological tricks. Or perhaps they serve a new function. To see photographs of some flies that have lost their halteres, check out the Braulidae (bee parasites) or Hippoboscidae ovinus (sheep ked). I love wingless flies. Did a presentation on them when I took entomology during high school … and have been creeped out and impressed by them ever since.

Colin Purrington Photography: Insects &emdash; snow-fly

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Antibiotic confusion in the Wall Street Journal

If you follow me on Twitter, you’ll know I have a thing against antibiotics. I love to take them when I have a bacterial infection, but I think it’s a terrible synonym for ‘antibacterial’, an older word that doesn’t mislead people into thinking the drug can work against viruses and other microorganisms. The problem with “antibiotic” is that people (as in “folks” who are not scientists, doctors, and science journalists) typically assume that they can treat non-bacterial infections, and this encourages people to demand antibiotics for anything that ails them. Part of this confusion is from the word itself (it sounds like it should work against all types of microorganisms). In addition to it sounding like it should be broad drug that can kill all things living, many dictionaries actually suggest exactly that, and that’s actually what the word used to mean. Unfortunately (and this seems to be the bigger problem), scientists, doctors, and science journalists don’t think “antibiotic” is at all confusing to lay people.

So last week I begged Ben Zimmer (Wall Street Journal) on Twitter to explore the origin of the word “antibiotic”, with the hope that people (folks and otherwise) would listen to him. Here’s his column: A Cure for ‘Antibiotic’ Confusion? It’s short and sweet, so just read it, but here’s my favorite sentence:

In current usage, “antibiotic” is roughly synonymous with “antibacterial,” though technically speaking antibiotics can act on microbes other than bacteria. [italics mine]

Two comments about the column.

First, I wish the article had explored just how common the confusion is. It’s not just that some people are confused. I think most people are confused. Again, I’m talking about “folks”, not the overeducated people who might be reading this nerdy blog post. But to be honest, some of the overeducated people I’ve talked to don’t understand antibiotic specificity, either. Because terrible word.

Second, Zimmer asked two people whether “antibacterial” could ever float as a substitute for “antibiotic”. They answered that it couldn’t because (essentially) the disinfectant lobby would object. That’s an odd reason because just as antibacterial wipes kill bacteriaantibacterial drugs kill bacteria. That’s because they both contain antibacterials, though the sources might differ. Zero conflict. Similarly, disinfectants and pills can contain antivirals. Or antifungals. And if there really was a conflict, I think the original use of antibacterial should trump the wipe lobby. Regardless, some scientists and physicians are already using “antibacterial” as synonym for antibiotic, so it’s not like there isn’t a precedent; it’s just too rare that they are doing so.

The issue is more that it’s hard for older people to avoid a word they have been happily using for their entire life. Good examples are “life preserver” (now “personal floatation device”) and suntan lotion (now “sunscreen” or “sunblock”), words that will probably only fully die when we do. But if properly motivated, people can make switches much faster. Two good examples are demonstrated by the employees of and Beaver College, now Google and Arcadia University, respectively. So I think a bunch of PhDs and MDs can summon the mental power to say “antibacterial” when speaking with impressionable patients or when designing outreach graphics. But they’ll only do so if some higher power (CDC, WHO) makes it clear that doing so might reduce overprescription of antibiotics. Even if using “antibacterial” would only reduce overprescription by 5%, the change would be worth doing.

I’m not suggesting that we stop using the word, “antibiotic”. The word is totally fine for conferences, publications, and situations where the context is clear or when there is plenty of time to clarify that they are antibacterials. The word is also invaluable when socializing with people from the powerful wipes lobby.

Thanks, Ben Zimmer!

Here are my previous posts on the topic, if you’re interested. If you conduct “science literacy” polls, you should read them. The reason is that asking something like, “Will antibiotics treat colds?” is a terrible question. You should be asking, “Do antibacterials kill viruses”. That will assess the science literacy more directly. Sticking with the old question just demonstrates that pollsters are unfamiliar with what “antibiotic” actually means.

You keep using the word antibiotic

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