Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
9/4/00
Contacts:
Donald Lewis, Extension Entomology, (515) 294-1101,
drlewis@iastate.edu
Elaine Edwards, Extension Communication Systems, (515)
294-5168, eedwards@iastate.edu
Yard and Garden Column for the Week Beginning September 8
Hummingbird Moths
By Donald R. Lewis
Extension Entomologist
Iowa State University Extension
Late summer is the time to enjoy another fascinating insect behavior in the home garden -- nectar feeding by large, dark moths that look like hummingbirds. This activity usually occurs around dusk, but may happen at other times of the day as well. Blossoms commonly visited are deep-throated flowers such as petunias and hosta blooms.
The moths in question have a body about the size of a hummingbird but no other physical resemblance to hummingbirds. What is remarkable is how much they behave like hummingbirds. These moths hover in mid-air and flit from one flower to the next. If you don't look closely at the dark color and the antennae at the front of the head, you can be easily fooled into believing these really are hummingbirds!
Sphinx Moths
The nickname hummingbird moth applies to several different species of sphinx moths. Sphinx moths, also known as hawk moths, are from the family Sphingidae. These are medium to large-sized moths with a large body and characteristic narrow, elongate front wings. The wings have the shape of a wide, flat triangle ending in an acute angle at the farthest point. Sphinx moths may have a wingspread of up to 6 inches though a more common size in Iowa is a 2- to 4.5-inch wingspan. There are approximately 125 different species of sphinx moths in the United States and Canada.
Sphinx moths are strong fliers with a very rapid wingbeat. They are capable of hovering in mid air for extended periods and flying just in front of flowers as they sip nectar through their extended proboscis. A tiny amount of nectar is withdrawn during a brief visit to each flower.
The well-developed proboscis of hummingbird moths is an extendable, beak-like hollow tube or tongue that may be several inches in length and often as long or longer than the moth's body. When not in use the proboscis is coiled against the underside of the head. The tightly spiraled proboscis is extended and held stiff by internal fluid pressure as the moth reaches for the nectar supply at the base of flowers. When the moth is done feeding, muscles coil the proboscis back into resting position. The rolling and unrolling action of the proboscis can be compared to the movements of a party noisemaker.
Hornworm caterpillars
The sphinx moths are the adult stage of the familiar hornworm caterpillars, named for the conspicuous "horn" or spine like process on the topside of the last body segment. The horn on a hornworm may look dangerous but it is harmless and the caterpillars do not hurt us. What they do to our garden and ornamental plants, however, often is quite destructive. Caterpillars such as the tomato hornworm and the catalpa hornworm are occasionally serious pests because of their voracious appetite for leaves.
The sphinx moth name for the adults of this group probably refers to a characteristic pose of some hornworm caterpillars. When disturbed, the caterpillars will elevate the head and thorax from the plant surface and assume a stance that vaguely resembles the Sphinx of Egypt.
Most, but not all, sphinx moths feed like hummingbirds. The most commonly observed hummingbird moth is the whitelined sphinx, Hyles lineata, so named for the broad white stripe running diagonally to the outer tip of each front wing. This is a stout-bodied, brown moth with a wingspan of 2.5 to 3.5 inches. The delicate pink coloration of the hind wings is visible when the moths are hovering at flowers. Whitelined sphinx moths are as likely to fly during the day as they are at twilight.
The caterpillar of the whitelined sphinx is a large hornworm that varies from bright green to almost black. A series of colorful yellow markings resembling eyespots line the length of the body. Don't feel bad if you are not familiar with this caterpillar. Very few people ever notice the caterpillar in spite of how common and abundant the moths can be in late summer. My limited experience has been to find whitelined sphinx caterpillars on Portulaca plants, both the ornamental moss-rose and the common weed purslane. Reference books list a wide diversity of plants as possible hosts, including apple trees "and other herbs and trees."
Only one sphinx moth, uncommon to Iowa, officially carries the name of hummingbird moth. The "hummingbird clearwing moth" is one of several moth species that lose most of the scales that cover and color the wings. The result of transparent or clear wings is a moth that resembles a very large wasp. The hummingbird clearwing is found in open woodlands and nearby fields.
The insect world is full of surprises. There are moths that look like hummingbirds and other moths that look like wasps. You're never quite sure what you're looking at!
ml: isugarden
Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.