The first characteristics to look for in identifying a butterfly cocoon are where it is found and how it is formed. Most butterfly cocoons are formed just large enough to house and barely cover the larvae. The majority of butterfly species will form cocoons that are loosely attached to leaves, branches or tree bark. If observed in these areas, it is most generally from the largest type of butterfly family, referred to as Papilionoidea, which include Swallowtails and Birdwings. Swallowtails are commonly found throughout Northern America and are native to the Ozarks, Oklahoma and the Southwest.
The Gulf Fritillary butterfly has a distinctive cocoon and looks like a dried-up leaf. It is a washed-out brown in colour. It is recognised by the spines formed on the cocoon. The larvae are poisonous if eaten and therefore avoided by most predators. The addition of passionflowers to many California gardens has expanded this butterfly to many areas in both the northern and southern regions.
If a bright jade green cocoon is seen hanging from a leaf, it is from the multicoloured and popular Monarch butterfly. As it evolves, it becomes transparent and changes colours to a darker brown with splashes of colour. Most all butterfly cocoons become transparent prior to becoming ready for the butterfly to emerge. This particular butterfly is prevalent in North America and frequently seen near milkweed plants, a popular food source.
The Parnassius butterfly caterpillar makes a flimsy cocoon. It is located near the ground, usually hidden among debris and is brownish in colour, to blend with the surroundings. When in the cocoon stage, it is the most vulnerable to predators.
If the cocoon found or observed is large and crudely built, it most likely belongs to the Skipper butterfly, a small moth-like butterfly. These cocoons are found on eaves of houses, in garages and sheds and generally anywhere the caterpillar finds to build its cocoon. They are traditionally larger than the other cocoons and sometimes expose a small portion of the pupae.
A butterfly larvae from the Gossamer-winged butterfly can be found on or near the ground and never really forms a true cocoon but instead a silvery shell. This butterfly has a rather intimate and unusual association with ants. The species has a bright iridescent and metallic colour. Commonly referred to as Coppers or Blues, they are native to Northern America with 46 species found in Idaho. This species of predatory butterfly larvae completes its formation within an ant colony, where it is nourished and protected by the ants. The butterfly itself is formed while still in among the ants and remains there for 3 to 4 weeks, prior to emerging from the ant colony, where it finally spreads its wings.