Tag Archives: entomology

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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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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Infestation of camel crickets

When it’s too hot to take photographs outside, I can always go down to my basement to photograph camel crickets (“sprickets” to many). I know, lucky me. But if you have a moist basement, you probably have them, too. The ones below are the introduced species (I think), Diestrammena asynamora, from Asia. They drive me nuts. So much so that I wasted time collecting ways to get rid of them (see my page, “Getting rid of camel crickets“, if you’re interested). The list is not 100% effective, as photographs attest, but at least I don’t have thousands of them anymore.

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

Colin Purrington Photography: Insects &emdash; Camel cricket (Diestrammena asynamora)

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Distinguishing tobacco and tomato hornworm caterpillars

After agonizing over the identification of hornworm larvae for years, I’ve developed two tricks that I’d like to share. Tobacco hornworm (Manduca sexta) caterpillars have stripes (seven of them), so remember that by thinking of Lucky Strikes cigarettes. Horn is usually red or red-tipped, like a cigarette. Also, tobacco gives you dark teeth and lungs … and tobacco hornworms have black shadows on their stripes. Tomato hornworms (Manduca quinquemaculata) have eight chevrons (Vs), which you can remember by thinking of V8 juice, which is primarily tomato juice. Here’s the graphic you can share with friends who might have it wrong:

Photographs of tobacco and tomato hornworm caterpillars

If you can, please spread the word … most of the tens of thousands of tobacco hornworm photographs on the internet are misidentified as tomato hornworms. Even Wikipedia page for tomato hornworm shows tobacco hornworm larvae (I’m working on it …). The problem is that tobacco hornworm eats tomatoes, and people with fancy cameras grow a lot of tomatoes.

For people living in Hawaii, please note that the above doesn’t include Manduca blackburni, which is closely related to tomato hornworm.

Photograph of tomato hornworm from Amanda Hill.

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Dangerous red light district for camel crickets

Further refinements to my camel cricket control setup.  Addition of a red “party light” illuminates the whole area so that the motion sensor works much better — no more motion-sensing lights in the system, as per initial design.  Note: most insects don’t see red well, so it’s just dark to them.  Just dab a little food onto the surface of the motion sensor, and they will come.  And then they will go.  Last night I caught approximately 30 crickets.  While I slept.  And upon waking, I could check my iPhone for the update from the WeMo app (I have it say, “Crickets sucked” at each event). Details on how to make your own. Two photographs below were taken by a Belkin Netcam HD automatically, when motion was sensed.  Again, all while I slept.

Camel cricket vacuum

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