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:

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