abdomen 
the hindmost of an insect’s three major body sections. The abdomen is the center for digestion and reproduction.

adult
a full grown, sexually mature insect.

antenna(e)
a pair of segmented sensory organs, one on each side of the head, used for sensing touch, taste, and smell. Commonly called “feelers”.

anterior 
located near or toward the head of an organism.

arthropod
animals of the phylum Arthropoda. All arthropods have a hardened exoskeleton, jointed legs, and a multi-segmented body. Examples: crabs, shrimp, spiders, scorpions, centipedes, millipedes, and insects.

butterfly 
an adult, typically day active member of the insect group Lepidoptera. Butterflies are often brightly colored and have antennae with knobs on the ends.

caterpillar 
an immature butterfly or moth. Also known as a larva.

complete metamorphosis 
the pattern of growth and change seen in the higher insects. It is characterized by the appearance of four distinct life stages: the egg, larva, pupa, and adult.

cuticle 
the hardened outer “skin” of insects. It is shed during molting.

dorsal 
located near or toward the back or upper surface of an organism.

dorsal heart 
the major pumping vessel of the insect circulatory system. In Manduca sexta it is visible as a dark dorsal line in late fifth instar (wandering) larvae.

egg
first stage of an insect

endoskeleton
supporting structure (e.g. bones ) on the inside of the body. Fish, amphibians, reptiles, birds, and mammals have endoskeletons.

exoskeleton 
supporting structure on the outside of the body. All arthropods have exoskeletons.

hawk moth 
a common name for moths in the same family as Manduca sexta (Sphingidae ).

head 
most anterior of an insect’s three main body section. The head is the center for sensory structures (e.g. eyes and antennae) and feeding.

head-cap 
informal term for a Manduca larva just before molting. Larvae at this stage look “bubble-headed”.

head capsule 
the hard exoskeleton covering the head of an insect. In Manduca larvae, this is one of the only truly hard sections of the body.

hindwings
the two rear wings of an insect.

host plant 
the variety of plant on which an insect prefers to live and eat. Manduca sexta host plants are in the Nightshade family (Solanaceae).

hummingbird moth
common name for another moth genus in the same family as Manduca sexta (Sphingidae ), which hover at flowers like hummingbirds.

insect
a class in the phylum Arthropoda. Insects are characterized by having six legs and three major body sections.

instar 
the period between larval molts. The first instar is the stage between the egg and the first molt, the second instar is the stage between the first and second molts, etc. Manduca sexta normally has 5 larval instars.

labium
the lower lip; a structure that forms the floor of the mouth.

labrum
the upper lip, which covers the base of the mandibles and forms the roof of the mouth.

larva
an immature insect. Butterfly and moth larvae are also called caterpillars.

Lepidoptera
the formal classification group (order) of butterflies and moths.

mandible(s)
insects’ first pair of jaws.

maxilla(e)
insects’ second pair of jaws. Maxillae also have sensory function.

meconium
fecal material that accumulates in the pupa that is eliminated when the adult emerges.

mimicry
the act of looking/acting like something else as a method of protection. Insects using mimicry can either mimic their surroundings so that they are less conspicuous, or deter predators by looking like something dangerous and/or distasteful.

molt
the process of shedding the exoskeleton.

moth
an adult, typically dusk – or evening – active member of the insect order Lepidoptera. Moths are usually less brightly colored than butterflies.

order
a category in the hierarchy of classification. This hierarchy is as follows: Kingdom, Phylum, Class, Order, Family, Genus, Species.

palp
a mouth feeler.

phylogeny
a “family tree” of organisms. Phylogenies show how organisms are related to each other. They can be generated using many different kinds of data, including DNA sequences and morphological characteristics.

posterior
near or toward the rear of an organism.

proboscis
the mouthpart of an adult moth or butterfly. The proboscis works as a functional siphon, enabling the insect to sip nectar from flowers.

protective camouflage
the act of blending into one’s surroundings to hide from potential predators.

pupa
one of the life stages of complete metamorphosis. Often referred to as a “resting” stage, since the insect is not walking around or eating. Nevertheless, complex metabolic changes are taking place throughout the pupal stage.

siphon
coiled, tubelike mouthpart of adult Manduca, used to sip nectar from flowers.

sphinx moth
common name for moths in the same family as Manduca sexta (Sphingidae). The name comes from the “Sphinx-like” posture many of the larvae will assume if disturbed.

spiracle
one of the “breathing holes” that run down the sides of an insect’s thorax and abdomen. Spiracles are the external openings of all insects’ respiratory systems.

stadium
stage in the life history of an organism.

thorax
the middle section of an insect’s body. The legs and wings attach to the thorax, making it the center for locomotion.

tobacco hornworn
the common name of Manduca sexta. The name comes from the spine-like horn on the posterior end of the larvae and the fact that the larvae feed on the leaves of tobacco plants.

ventral
near or toward the “belly” of an organism. (opposite of dorsal )

wandering
the walking behavior of late 5th instar Manduca larvae, just before pupation.

Larvae, also known as caterpillars, hatch from their tiny, pale green eggs three to five days after the eggs are laid. These “newborn” or first instar larvae are only a few millimeters long and very pale green, but that changes quickly. As the larvae get older and larger they become bright green with seven pairs of lateral white stripes bordered with black. At the hind end of the body is a horn or spinelike process that is usually red or reddish-brown. This horn is characteristic of most species in this family of moths, and serves as the basis of another common name: the tobacco hornworm. It is not clear what purpose the horn serves, although there is speculation that it may be useful in protective camouflage or mimicry. One thing it does not do however, is house a stinger, although it is a common myth that it does.

How many legs?
According to the picture, Manduca larvae appear to have eight pairs of legs. Aren’t insects supposed to have just three pairs? The three pairs of legs on the thorax are the true legs. These will become the six legs of the adult moth. The larvae’s stubby prolegs complete with claw-like “crockets”, are part of the abdomen. They are used for crawling, clinging, and climbing ,and are changed into other structures during metamorphosis.

The name Manduca means “glutton” or “chewer”. Looking at the larvae, it’s easy to see where this name comes from. The larvae have mouthparts adapted for chewing, and they put these to use eating everything in sight. In the wild, they feed voraciously on such plants as tobacco, tomato, potato, pepper, and nightshade (Family: Solanaceae). Gardeners familiar with this insect know that a mature (5th instar) larva can consume an entire tomato or chili plant in a single night!

It’s important to note that the larvae don’t eat all the time. Right before each larval molt, the larvae stop eating and void their gut contents so that they’re empty for the actual molt. During this phase, which can last 48 hours or more, the old hard head capsule slips forward to make room for the developing new one.

The larvae appear bubble-headed at this point and are informally referred to as head-caps. Eventually, the old skin (exoskeleton) is shed and is usually eaten by the larva in a perfect example of recycling. The molting process repeats itself four times, with each successive molt yielding a larger larva.

At the end of the fifth and final larval instar, something different happens. The huge larva climbs down from its host plant and begins a period of vigorous walking or wandering that typically lasts for about five days. During this stage, gut contents are again voided, body moisture is lost, and a dark bluish line or dorsal heart becomes visible along the larva’s back. At this point, the larva Manduca bury themselves about 9 – 15 inches deep underground, in loose soil or leaf litter. This protects them from predators and the weather. After a few days, the buried larva molts a final time to form a light green pupa.

The tobacco hornworm Manduca sexta is a wonderful experimental animal that is used in the study of a diverse array of biological problems at research institutions around the world. This insect has proven invaluable for helping to answer questions ranging in topic from basic ecology and growth, to neurobiology, muscle physiology and the biochemistry of camouflage.

The Manduca Project is based in student explorations of Manduca sexta, and has proven that this insect is important not only as a research subject, but also as a strong bridge between scientists and students.

To date, thousands of students have studied Manduca sexta in the classroom, designing experiments, composing poetry and songs, writing daily entries in their journals, and even involving family members.

We have high hopes that teachers using these materials will continue to share their ideas with us and with each other, especially as we increase our efforts to introduce it to a wider audience across the Internet.