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Caterpillars
Let's get familiar with the caterpillar body structure. Basically most butterflies and moths caterpillars are long cylindrical in shape. The primarily mission is to feed and grow. It can only grow a little bigger and have to moult. Most butterflies will moult four to five time then will turn into a pupa.
Head - One the caterpillar head there are six simple eyes, or known as stemmata or ocelli, on each side. Caterpillar does have antenna although very small and hard to be seen. There is always the inverted 'Y' shape on its face. It is the mouthpart, include the mandible, maxillae and palp similar to the chewing mouthpart of grasshopper. At the bottom of the head there is the spinneret which produces the silken thread. Not many caterpillars have this special glandular osmeterium. When disturbed, the caterpillar display the osmeterium from it head, which is brightly red colour and quite scarily. Together there is the pungent smelling and strange enough to drive the predator away.
Thorax - The thorax is three segmented, each has a pair of tharacic legs. There is a pair of spiracles on the first thorax segment but not on the other two segment.
Abdomen - There are the segments in the abdomen. There are the spiracles on each side of the first eight segments. Segment three to six each have a pair of ventral prolegs. The last segment also has the similar prolegs known as anal prolegs. Each proleg has a crochets which help in walking and holding objects. When walking on he smooth surface, the crochets act as suction cups. Some caterpillar bodies are smooth but most are with minute spines, called spinules.
- Orchard Swallowtail Caterpillar, last instars
- Orchard Swallowtail Caterpillar, last instars
