Tomato hornworm....

Tomato hornworms can be up to 5 inches long—which can be quite a shock when you first come across one! They do the most damage in the caterpillar, or larvae, stage. They are pale green with white and black markings, plus a horn-like protrusion. (They are not capable of stinging.) The life cycle is as follows:

• In late spring, large adult moths lay eggs on the undersides of foliage, which will hatch within a week.
• Caterpillar larvae will feed from 4–6 weeks before creating a cocoon for overwintering in the soil. If the weather is warm enough, larvae may only burrow for as little as 2–3 weeks.
• Moths will emerge in the spring, and can be identified by their orange markings. They will then lay eggs once again. More than one generation a year may be possible in warmer climates.

The larvae blend really well with the plant greenery. Just get used to a daily patrol, looking for hornworm eggs and small caterpillars. Here are some cues of infestations:

• Look closely at the TOP of your tomato leafs for dark green droppings left by the larva feeding on the leaves. Then look at the underside of leaves and you'll find a hornworm.
• Look for stems missing some leaves and wilted leaves hanging down. You may find white cocoons and their hornworm hosts nearby.
• Look for an entire tomato plant disappearing while you are at work.  These guys are voracious.