Green Caterpillars in the Garden

By Evan Sandsmark - February 6, 2013 317 recent views

A little while back a reader sent us a photo of a green caterpillar in his garden. He’s found several of the green caterpillars as of late, and he was seeking more information about them. The reader has already done some research and indicated that he thought he found “tomato worms” (based on other information, we can confidently assume he meant “tomato hornworms”, which are actually caterpillars), in large part because the creatures were on his tomato plant. He was most puzzled about the webs they seemed to be spinning for themselves, and he also wondered if the “worms,” once enmeshed in a web, had died. What are these green caterpillars, if they even are caterpillars, and what’s the deal with the webs they are creating?

Before we attempt to answer these questions, let’s take a look at the picture our reader sent:

Green Caterpillar

As the reader immediately points out in his email to us, if he is in fact finding tomato hornworms, it is curious that the creature pictured above has no horn on it. Tomato hornworms, which are the larval forms (caterpillars) of five-spotted hawkmoths, occasionally do not have very pronounced horns, but they always seem to have horns, horns that are actually quite noticeable. (We are, to be trite, talking about tomato hornworms, after all.) Moreover, tomato hornworms have very pronounced V-shaped patterns on their bodies. In the picture above, we should be able to clearly see white V shapes on the creature’s back, but this doesn’t seem to be the case.

These problems with the “tomato hornworm” hypothesis, however, can be met, as it may simply be the case that our reader found an immature tomato hornworm, which might not have a horn and V-shaped pattern on its body, or at least they might not be very noticeable. Often a plant that is afflicted with hornworms will have several different creatures on it of various ages, however, so it would be strange if every caterpillar our reader found had no horn, which seems to be what our reader implies (although his language is ambiguous on this point).

Despite these reservations, we still think there is a fairly good chance our reader did find tomato hornworms. He found green caterpillars on a tomato plant that look a like tomato hornworms – what else can we conclude? However, we do remain puzzled by the webs that our reader is finding. Some caterpillars do spin webs – for instance, tent caterpillars and fall webworms are prolific web spinners that more or less operate in the way described by our reader – but as far as we know tomato hornworms do not. Building webs is part of the life cycle of tent caterpillars and fall webworms (in that they both build “tents” that they feed in), but this is not the case with hornworms. For this reason, it is possible our reader found fall webworms (or a related caterpillar) because they partially resemble the creature pictured above, but overall the image matches a tomato horworm more than a fall webworm.

So, we must conclude with some uncertainty. There are compelling reasons to think that the green caterpillar our reader found is a tomato webworm, but we are unsure why our reader is finding them in webs. Perhaps they are caught up in spider webs, and in which case they might be dead or on their way to death. However, the reader describes the webs as “around” the caterpillar, as if the caterpillar made it, and we really don’t know why this is the case, which leads us to add that perhaps our reader found a caterpillar that is, or is closely related to, a fall webworm. With this information, perhaps our reader can look into the situation further to figure out exactly what he found.

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  1. Dan says:

    What you have there is not a tomato hornworm it is in fact what most people know as an inch worm. Really There is quite a bit of difference between the two and they are vastly different even at the juvenile stage.

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