full set of six true legs and ten prolegs
Caterpillar of Psalidostetha banksiae,
All caterpillars have 3 pairs of true legs attached under the thorax. The true legs are segmented, with joints like our knees and ankles. They each have a little claw on the end.
Many caterpillars also have 5 pairs of prolegs, like Psalidostetha banksiae pictured above. The prolegs are not segmented, but are cylindrical stumps. They are used for walking and clinging, as they have a set of microscopic hooks on the base (crochets). The last pair of prolegs on the anal abdominal segment are usually called claspers. With 3 pairs of true legs and 5 pairs of prolegs, these caterpillars walk with a sort of ripple movement.
The larvae of other species of insects such as wasps and flies can have more than 5 pairs of prolegs.
full set of 3 pairs of true legs|
but with 7 pairs of prolegs :-
Larva of a Sawfly,
(not a true caterpillar)
Photo: courtesy of Jenni Horsnell, Wagga Wagga
Some species in different families have caterpillars with fewer prolegs. The number of prolegs is a constant throughout its life as a caterpillar, depending only on the species. These caterpillars move in a looper motion.
only 4 pairs of prolegs|
Caterpillar of Anomis flava,
only 3 pairs prolegs|
Caterpillar of Chrysodeixis eriosoma,
only 2 pairs prolegs|
Caterpillar of Scopula perlata,
Some have no prolegs at all, and move in a slug-like motion.
upside down Caterpillar|
showing no prolegs at all
of Doratifera vulnerans,
In the metamorphosis, in the pupa, all the prolegs disappear. However, the six true legs on the thorax are retained through pupation, and are transformed into the legs of the adult for most families of butterflies and moths.
But, over the millenia of evolution, one pair of true legs has atrophied for the butterfly species in the family NYMPHALIDAE, so that they have only four legs, for example:
(updated 11 April 2013, 23 November 2018, 26 May 2020)