Parasa lepida caterpillar on Mangifera Indica

Parasa lepida caterpillar on Mangifera Indica

Seen at 2019-08-15T05:00:00Z

This is called a slug caterpillar. The name is a local name and not a proper taxonomic one. This local name is due to the fact that the underside appears like a slug although this is the larva (caterpillar) of a moth. The caterpillar belongs to the family Limacodidae. I would like to know the species.
The individual that you can see here is in its final instar. I haven’t reared these ever so I cannot give more information about the instars.
Fun Fact 1: Often after the monsoon you will see many clusters of large oval, egg like structures on the bark of mango trees. The egg like structures are cocoons and are made by these “slug caterpillars”.
Fun Fact 2: Stay away from touching this caterpillar. All the bushy hair that you see in the image are uricating. This means that each carries a tiny droplet of an irritant. When you touch the caterpillar, the droplet is injected in the skin and can cause fairly serious pain. I would love to swipe this caterpillar with a Ph paper. Why?
Fun Fact 3: See the colors, they are bright and gaudy. This caterpillar makes no attempt to hide. This is because of its defense mechanism (The urticating hair).

Do you know any other creatures that advertise their defense?


please give a reference of it calling it a slug caterpillar… It is really interesting and flickering colors it bears on it and if you say it is not for defense the what are this colors for? @VirenVaz @Arunan @Akshitha @G_N

Bivas, as I said the name is a local name not a scientific one. Other than saying that the caterpillars belongs to the Limacodidae family I can’t say much. Here are my justifications for placing it in the Limacodid family

  1. Prolegs converted to suckers
  2. Cocoon in the form of hard oval shell like structure.

I’ve mentioned the defense mechanism is the urticating hair. The coloration is just to warn predators of the fact that the caterpillar is “nasty” to eat. Oh and the colors don’t flicker, they are just bright.



Parasa lepida, the nettle caterpillar or blue-striped nettle grub, is a moth of the family Limacodidae.

@bivasnag @VirenVaz


Will these so many defence mechanisms still exist when it will become a butterfly/moth? It would be interesting to know what does its adult stage look like? Or where do all these defences go?

We cannot touch it, but we can observe it.

Thanks a million.
I’ve seen the adult too. But never snapped it.


Do post the picture if you ever come across the adult again :smile:

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The adults lay their eggs on the plants the larvae feed on. Caterpillars are very slow moving and normally do not move from the host plant. Hence, they are easy prey and these defence mechanisms are a necessity. Once it metamorphoses into the adult, most of these defence mechanisms are not necessary as they can get away from the predator by means of flight. They do have other defence mechanisms such as camouflage or mimicry.


@jaikishan, maintaining a defence mechanism has some “cost” associated to it. In a caterpillar it means that some amount of energy and nutrition must be diverted from growing in size to synthesising the chemicals and growing the hairs itself.
When these type of caterpillars pupate the hair is dropped off and actually become part of the cocoon, still serving as protection.
An few questions to myself here are…
How do you know if the hairs are really urticating or not? Maybe the caterpillar is faking it?
Maybe I should touch one and see?
Is there a better way of checking for urticating hair?
Can the CUBE lab help test for urticating hair?


True, we need to know what happens to these defense mechnisms and how exactly they are lost? Or are they not lost but transformed into something else?

It does look like a defense mechanism, but there are other larvae especially of fruit flies which dont show any such defense mechanisms but still survive in wild.

We also need to find out these hairy structures act against which predators, it most likely should be documented in literature.

Once caterpillar becomes adult, do these hairy structures become part of its own body? In that case how, as they all are covered with irritant, i think acid, wont it harm caterpillar when it transforms into adult?

@VirenVaz @Akshitha @bivasnag

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There are many species even among lepidoptera (butterflies and moths) that do not have poison hair as defense mechanism. They bank on camouflage, speed, startle and many other methods to deter predators. No defence is complete, I’ve seen mynas catch these hairy caterpillars and bash them till most of the hair drops off and then eat them. So evolution takes care of numbers all around.

The caterpillar sheds its skin (exoskeleton) for the last time during pupation. Just before pupating though, it builds a cocoon, the hair drops off and is incorporated in the lining of the cocoon.

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The question can be framed as,
Why caterpillars dont get harmed by their own hairs?
Not sure if caterpillar has exoskeleton?
Adults are known to have exoskeleton.
You may be meaning pupal case is shed, and hairs are also shed at that time!

I don’t know if this statement itself is true. And from it stems more questions. If we poke a caterpillar with a hair from its own or another caterpillars body, how will we be able to recognise the reaction (if any) between, a reaction to something poking it or a reaction to the chemical in the hair. I’m not at all sure how i would frame this research question.

I’m sure :wink: If you define a skeleton as a structure that gives support to the body then all insects and I think all arthropods are supposed to have exoskeleton.
Basically its the stuff that keeps their insides inside.
Adult also do have exoskeleton.

No Jai, I’m saying that the caterpillar, in the final instar (caterpillar stage) will break of hairs and integrate them into the cocoon which acts as a defense. Once the cocoon is built, the final instar caterpillar will shed its exoskeleton inside the cocoon and pupate. The pupa is naked.


Caterpillar has hairy structure on their body which has irritant chemicals, but caterpillar is also exposed to its own irritant.
How it is not getting harmed by its own irritant?
Why it is harmful to other organisms and why it is not harmful to caterpillar itself?

This would be a great entry into the area of immune systems.

Any reference to support this claim?
If thats true that all hairs with irritant chemical are shed into cocoon, why it is not getting harmed by that chemical?
How does irritation/inflammation happen?
Do caterpilars get irritation/inflammation?
Is their any involvement of antigen-antibody reactions?

This model could be great initiation into area of immune system.

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@jaikishan what say we try to design an experiment? I’m sure I could get my hands on some hairy caterpillars. But I don’t know how to continue. Any thoughts?
I came in contact with a few of them 2 days back. It’s still scratching.


Yes, lets try to do some literature search, whether caterpilars do get irritation or are they immune to it?

Are there already any such study reported in literature?

why does it cause inflamation? What kind of immune response is triggered?
Does caterpilar has ability to differentiate its self antigen from non-self antigen?
Are there any anti inflammatory compounds present in caterpillar which prevent inflammation from its own self antigen… that can actually be of medical importance.

There are various methods inorder to determine what type of immune cells are activated, and can be done under laboratory conditions.

This can be a project nationwide, where people can look around for hairy caterpillars.

Also we may have to make sure precautions necessary for this type of study.

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