Butterfly Larvae

Butterfly Larvae

Larvae, or caterpillars, are multi-legged eating machines. They consume plant leaves and spend practically all of their time in search of food. Caterpillars mature through a series of stages, called instars. Near the end of each instar the larva undergoes a process called apolysis, in which the cuticle, a mixture of chitin and specialized proteins, is released from the epidermis and the epidermis begins to form a new cuticle beneath. At the end of each instar the larva molts the old cuticle, and the new cuticle rapidly hardens and pigments. Development of butterfly wing patterns begins by the last larval instar. Butterflies belong to the specialized and prolific lineage of holometabolous insects, which means that wings or wing pads are not visible on the outside of the larva, but when larvae are dissected tiny developing "wing disks" can be found on the second and third thoracic segments, in place of the spiracles that are apparent on abdominal segments. Wing disks develop in association with a trachea that runs along the base of the wing, and are surrounded by a thin "peripodial membrane", which is linked to the outer epidermis of the larva by a tiny duct.

Wing disks are very small until the last larval instar, when they increase dramatically in size, are invaded by branching tracheae from the wing base that precede the formation of the wing veins, and begin to express molecular markers in patterns associated with several landmarks of the wing. Near pupation the wings are forced outside the epidermis under pressure from the hemolymph, and although they are initially quite flexible and fragile, by the time the pupa breaks free of the larval cuticle they have adhered tightly to the outer cuticle of the pupa (in obtect pupae). Within hours the wings form a cuticle so hard and well-joined to the body that pupae can be picked up and handled without damage to the wings.

Butterfly larvae ( caterpillars) are quite variable in color and shape. Basically, they have a well – developed head, 3 thoracic and 10 abdominal segments. The head has simple eyes ( ocelli ), a pair of 5 segmented legs or true legs each, which endin a curved claw. The abdomen normally hears 5 pairs of prolegs of false legs on segments 3 to 6 and on 10. the first 4 pairs are called abdominal legs and the last pair the claspers. These prolegs are fleshy, more or less conical, retractile and flattened and have a series of hooks or crochets which help the larva in locomotion. Nine pairs of spiracles or respiratory pores are borne respectively on the prothoracic and irst 8 abdominal segments. The last segment carries a sclerotised plate called surnal plate or button of silk for pupal attachment. The larval skin or cuticle is soft and flexible and may be clothed with spines or setae (bristles) ina few cases.

The larvae mainly feed on leaves of flowering plants. They are very specific in their feeding habits and will usually only feed on a few closely related plant species. Larvae recognize their host plants by certain aromatic vegetable oils, which they contain. It is generally believed that selection may depend upon the detection of chemical attractants in the food species and of repellents in others.

After spending most of its days eating continuously the larvae forms a Pupa