There are three distinct body that the larva has. There is a
head, a body with a thorax and an abdomen. The head has a pair of very short antennae, a mouth opening (upper lip, mandibles, and lower lip), and six pairs of very simple eyes, called ocelli. Even though the caterpillar has many eyes, still their vision is poor. The antennae helps the monarch fir guidance and the maxillary pulps, which are sensory organs helps direct the food into the larva's jaws. (see image)
The thoracic segment includes two pair of jointed legs while some of
the abdominal have false legs, or prolegs. There are usually five
pairs of prolegs that have tiny hooks on them so that they can hold the
larva onto its silk mat or leaf. Monarchs have fleshy tentacles at
the front and rear ends of their body that functions as a sense of organs.
Monarchs obtain oxygen through holes in the sides of their thorax and
abdomen called spiracles, just like the other insects. The spiracles
are connected to a network of long-air tubes called trachea so that it
can carry oxygen through the body.
