Do Butterflies Bleed When They Hatch From Their Cacoon?

Butterflies do not bleed when they hatch from their cocoons, instead they release stored up waste products that are blood reddish in colour. It is a very natural part of the process. In Medieval times this blood was seen as a bad omen that something terrible was going to happen soon.

A cocoon is a casing that is spun of silk by many moth caterpillars as well as numerous other holometabolous insect larvae. The cocoon is spun in order to act as a protective covering for the pupa. These cocoons can be hard or soft, opaque or translucent. Depending on the type of insect larva producing it they can be solid or meshlike, of various colours and composed of multiple layers. There are some moth caterpillars that will shed the larval hairs and incorporate them into the cocoon that they are building. In some cases these are urticating hairs and these can cause the cocoon to be irritating to the touch, therefore deterring potential predators. Other larvae attach fecal pellets, pieces of vegetation or small twigs to the outside of their cocoon, this can help attempt to disguise it from predators. Some larvae spin their cocoon in a location that is concealed, either on the underside of a lead, in a crevice, near the base of a tree trunk, concealed in the leaf litter on the floor or suspended from a twig. The silk moth produces silk in its cocoon that can be unravelled to get silk fibre. This process makes this particular moth the most economically important of all of the Lepidopterans. The silk moth is also the only completely domesticated Lepidopteran and is never found in the wild.

Making the cocoon is one thing but insects that pupate in a cocoon also need to be able to escape from it. This can be done by the pupa either cutting its way out of the silk or by secreting fluids that soften the cocoon. The latter is often the waste products that may be mistaken for blood.

It is common for a butterfly to "bleed" from it's bottom when it hatches from the cacoon, but it isn't blood.  It's waste that is stored up that is red in color.

I was also surprised to see this waste product when my daughter did her first butterfly kit.  I guess I shouldn't be surprised because we humans also have a similar thing happen when we are born.  This by-product, even in butterflies, is called meconium.  It's the first few bowels movements in an infant and is a thick tarry blackish color.  Now, even as a newborn baby nurse, did I ever put much thought into that "meconium" as being a "by-product" of our development during pregnancy.  (Yuck?)  But I suppose it is.  As this is how it was explained on the butterfly kit.  It's not anything to do with blood, but part of the beautiful colors that make up the butterfly.