Category Archives: Education

Nictitating membrane in a sharpie

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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

 

Distinguishing tobacco and tomato hornworm caterpillars

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Tobacco hornworm (Manduca sexta) caterpillars have stripes (seven of them), so remember that by thinking of Lucky Strikes cigarettes (seven is a lucky number; stripes sort of rhymes with strikes). Plus the horn on a tobacco hornworm is usually red or red-tipped, like a cigarette. Tobacco hornworms also have black shadows on their stripes, and and tobacco gives you dark teeth and lungs.

Tomato hornworms (Manduca quinquemaculata) have eight chevrons (Vs), which you can remember by thinking of V8 juice, which is primarily tomato juice.

Here’s a graphic that summarizes the above:

Photographs of tobacco and tomato hornworm caterpillars

Here’s a larger photograph of a tobacco hornworm (7 stripes, red-tipped horn) covered with Cotesia congregata pupae.

Manduca sexta