AUGUST
2002

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

8-22-02

Mischievous Moths Masquerade as Hummingbirds

What's not to like about hummingbirds? These beautiful little birds are one of the true miracles of nature. They zoom about our flowers in search of nectar. They are more than happy to accept a free handout at hummingbird feeders. And much to our delight, they stage spectacular aerial battles in quarrels over food or territory.

There are moths that look and behave much like hummingbirds. These insects do an excellent job of mimicking hummingbirds--such a good job, in fact, that they are called hummingbird moths!

However, that is not the only common name used for these bird mimics. They are also called hawk moths. This bird name is apparently based on their ability to fly rapidly. Some of these moths can fly more than 30 miles per hour.

Another common name for these insects is sphinx moth. This name is derived from the behavior of the larval stage of the insects. When disturbed, the larvae sometimes rear up, presenting a visual image that resembles that famous statue in the Egyptian desert.

Most of us are probably more familiar with hummingbird moths when they are in the immature stage rather than in the adult stage. Caterpillars of hummingbird moths are known as hornworms. There are a lot of species of hornworms, and all of them have a single horn on their rear ends.

One of the most common is the tomato hornworm. This is a large, green worm that feeds on tomato plants. Most tomato hornworms are discovered when a gardener notices that the leaves on tomato plants have disappeared. Those leaves have been devoured by the hornworms.

Once the hornworm reaches mature size of about 3 inches in length, it crawls down from the plant and digs into the soil. Once in the soil, the caterpillar fashions a cell, complete with cement-like walls. There, the caterpillar turns into the pupal stage. The pupa is brown or black in color and is sometimes discovered by gardeners when they plow the soil. The pupae that develop in the fall spend the winter snug in their soil cells.

The following spring, pupae that have survived the chill of winter change once again. This time, the miracle of insect metamorphosis results in the adult insect--the hummingbird moth. The moths then show up sipping nectar from flowers.

Flowers that are attractive to hummingbirds are also attractive to their namesake moths. The long beak of the hummingbird allows it to extract nectar from flowers while hovering in front of the blossom. The hummingbird moth feeds in the same manner, also using a long feeding tube. But the moth coils up its mouthparts when not in use.

Some of the hummingbird moths are about the same size as hummingbirds. Since the two creatures also share similar coloring and behavior, it is easy to see why they are sometimes confused with each other.

There are many species of hummingbirds, and they range in size and color patterns. So it is with hummingbird moths. These moths also feed on various food plants as caterpillars. The tomato hornworm commonly feeds on tomato, as the name suggests, but, in addition, it also feeds on tobacco and potatoes. There is a paw paw sphinx, an elm sphinx, a sage sphinx and a cypress sphinx, and they are all hummingbird moths. The catalpa sphinx larvae, as you guessed, feed on catalpa, and make good fishing bait.

One unusual group of hummingbird moths lacks scales between the veins on the wings and is called clearwing hummingbird moths. Several have yellow and black coloring and mimic bumble bees. Many groups of insects are good bee mimics, but only within the hornworms do we find mimics of both the birds and the bees!

 

Writer: Tom Turpin
Editor: Olivia Maddox