Digestive System
In Adults:
Butterflies are designed to handle a liquid diet. An organ called the pharynx at the base of the proboscis, expands to create a partial vacuum, allowing liquid to be drawn up the length of the proboscis. The food is then pushed through the thorax and into the abdomen by contracting muscles that line the digestive track. Food can be stored in an organ called the crop until it is needed. At that time, the food travels to the midgut where the nutrients are digested and absorbed by the blood or stored as fat. After the midgut the remaining water is absorbed by the hindgut and rectum.
Respiratory System
For the Egg:
Exchange air through tiny water-repellent pores through their shell. The egg can have as many as 14,000 pores covering as much as 12% of the eggs surface area. These pores work so well that eggs can survive even if they are flooded.
For Larvae and Adults:
Organs for breathing are located in the abdomen. This is also where butterflies take in oxygen. Unlike animals that use lungs or gills, insects breathe through a much simpler passive respiration process.
Butterflies have series of small pores on either side of the abdomen, called spiracles, that are used to draw in oxygen. Inside, a series of tracheal tubes channel the air to different parts of the body.
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Nervous System
Butterflies have a simple nervous system. Nerve cells are grouped in clusters called ganglia. One of these, in the head, is usually called the brain. It connects to a nerve cord, which runs the length of the body, passing through other ganglia along the way. There are two additional ganglia in the thorax and four in the abdomen. From these nerve clusters, smaller nerves extend to all parts of the body, where they control motion, circulation of hemolymph, digestion and reproduction.
NOTE: The nervous system runs throughout the butterfly's entire body.
Reproductive System
The reproductive system is located in the abdomen. Each butterfly has a pair of gonads – ovaries or testes – and a series of ducts that carry eggs or sperm to the outside of the body. Male butterflies have a pair of claspers at the tip of the abdomen. These are used to hold the female during mating.
After mating, sperm are retained in a special organ in the female called the bursa. Eggs are not actually fertilized until just before they are laid.
Circulatory System
Butterflies and other insects do not have closed circulatory systems consisting of veins and arteries like humans do. Instead, the internal organs of a butterfly are bathed in blood – called hemolymph – that circulates within the entire body cavity. A long tubular heart moves the blood throughout the body.
NOTE: The circulatory system runs throughout the butterfly's entire body.
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