Unfolding moth mysteries

Emperor moth

The word moth can give you an impression of very dull, dry and sometimes scary looking insects that fly around your bulbs/ tubelights.  However, in reality, moths are extraordinarily colourful insects and have huge ecological roles – from acting as pollinators for plants to being prey for birds, bats and other animals! Many-a-times, people refer to butterflies and moths interchangeably.

 

 

Incidentally, some of the butterflies can also look pretty dull, like this Evening Brown butterfly –

My recent trip to Bhimashankar WLS (Maharashtra) left me in awe about the sheer numbers and the diversity of moths that we saw in this area. I have visited this sanctuary way back in 2002 and 2003 and it was almost the same scene back then. Somehow this place has always made me fall in love with these nocturnal creatures, which are usually ignored amongst the other charismatic and colourful fauna. These moths gave us a colourful show on both the nights that we were there and some of them showed up during the day as well. While we watched the show, there were many questions that rose in each of our minds and we kept quizzing each other about more information on these creatures. I realised that ‘moths’ was a grey subject that many people didn’t have much clarity on, including myself. Hence, when I got back home, I searching the internet and found there is great paucity of information on these tiny insects, their species-level identification and behaviour.

This inspired me to write this blog in order to put together some of the unresolved mysteries in our heads and my understanding of the answers after reading up the reference materials available online. I’ve used an FAQ format to put together this blog.

What are moths?

The word ‘moth’ was used in the 17th century to mean someone who was apt to be tempted by something that would lead to his or her downfall. Which is where the saying comes ‘Like a moth to a flame’. Moths are insects which belong to the order Lepidoptera (means scaly winged; this order includes moths and butterflies). Approximately about 265,000 species of moths and butterflies are believed to exist on this planet out of which 160,000 are believed to be moths; many of which are yet to be described. The life-cycle of a moth is very similar to that of a butterfly i.e. Egg – Caterpillar – Pupa – Adult.  The first fossils of lepidopterans are known to be found about 190 million years old.How do I distinguish a moth from a butterfly?Here are a few simple tips to distinguish a moth from a butterfly by looking at its physical characteristics:

1. Check the antennae – Butterflies have slender antennae that are club-shaped or hooked at the ends whereas moths have slender antennae with no club-shaped ends. Some moths also have hairy or feathery antennae.

2. Check the body structure– Moths tend to have a stout and hairy looking body with thicker scales whereas butterflies have a thinner and smoother body.

3. Time of activity – Most moths are nocturnal or crepuscular while most butterflies are diurnal. However, there are exceptions to this rule for both.

Moths

Feathery antennae

Thin antennae (no club-shaped ends)

 

Butterflies

Clubbed antennae

Hooked antennae

 

Some of the behavioural characteristics are as follows:

4. Butterflies mostly rely on vision to find mates whereas moths rely mostly on scent to find mates. This is why some moths have a feathery antennae to pick up scent/ smell of their mates. 

5. Butterflies warm their body by basking in the sun. Moths vibrate their muscles internally (called shivering) to produce heat while their thicker scales insulate them.Some butterflies also look like moths, for e.g. –

Moth

Butterfly

 

Why do they fly at night?

Moths have an internal mechanism (thermogenesis) to warm up their bodies which does not require sunlight (unlike butterflies). One other logical reason that I’ve come across is that there is less competition for food if they’re nocturnal, since there are butterflies flying during the day. Also, perhaps because there are fewer predators at night.What do they feed on?

As adults, moths do not have mouth parts to chew any food (similar to butterflies). Hence, they also survive on liquid diets like nectar from flowers, juices from fruits, etc.

Uranid moth

Why are they attracted to artificial light?

A light trap set up to study moths

Moths get attracted to artificial light and are often seen circling around bulbs and tube lights. One hypothesis to explain this behavior is that moths use a technique of celestial navigation called transverse orientation. By maintaining a constant angular relationship to a bright celestial light, such as the moon, they can fly in a straight line. Celestial objects are so far away, that even after traveling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field, or on the horizon. When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon. (Content source: Wikipedia).

** One of the methods to study moths is to set up light traps by putting up an artificial light above a white cloth and wait for the moths to get attracted to the cloth. Then photograph it individually and also do an average count each night.Why are moths so dull?
One of the reasons is that many moths attract mates through smells (pheromones) and many butterflies attract mates visually. Here is an example of how a dull moth can look bright and colourful when it opens its wings.

Dull coloured wings (forewings) seen when at ease

Bright colours of the hind wing seen to threaten an approaching predator

How does a moth save itself from predators?

This behaviour is called the defense mechanism. Moths can use colours and patterns on their wings to scare away predators. Some moths have special markings while others may have large eye-like markings. There are few others whose hind wings are brightly coloured, which are hidden under their forewings while they’re at ease (seen in the above images). Some of them even secrete a kind of smelly liquid when under threat or stress (images below).

Skull-like marking seen on the Death’s-head Hawkmoth

Smelly liquid being secreted when under threat

However, moths are actually quite colourful creatures with intriguing patterns, if you’ve ever managed to watch them closely!

What is the significance of moths in the ecosystem?

•          They act as pollinators for many fruiting and flowering plants.
•    They play a key role in the food-chain since they’re prey to birds, bats, lizards and other insectivorous animals. The caterpillars are also eaten by smaller mammals like rodents, cats etc.
•     They’re indicators of a healthy ecosystem. Areas rich in butterflies and moths are also rich in other invertebrates.
  
  

  Humming bird moth

Moth Caterpillars (mostly hairy) –
 

 

All-in-all my recent trip to Bhimashankar WLS brought in some nostalgic memories of having seen my first Moon moth, my first Death’s-head Hawkmoth etc at the dhaba (local eatery). Here are some moth images taken during my trip –

Death’s-head Hawkmoth

Day flying moth

Owl moth