The Moth and the Butterfly

This article contrasts two of the world’s most beautiful insects, namely the moth and the butterfly, both belonging to the insect Order Lepidoptera. Although somewhat similar in appearance, there are many physical as well as behavioural characteristics that differentiate moths and butterflies.

Before contrasting the physical differences between these insects, it is first worth noting that insects of the Order Lepidoptera that are active during the daytime are most likely to be butterflies, which account for approximately 10% of all Order Lepidoptera’s species.  Conversely, those that are active at night are most likely to be moths, accounting for approximately 90% of all Order Lepidoptera’s species.

Larval and Pupal Stages:
All moths and butterflies go through a process known as complete metamorphosis, whereby an insect undergoes a four-stage change in anatomical and physiological form through a series of life stages.  Both moths and butterflies develop from egg to larva to pupa to adult.

Both moths and butterflies are caterpillars in the larval stage, with most moth caterpillars being fuzzy in appearance, in contrast to butterfly caterpillars, which are not. 
The pupal stage of metamorphosis for butterflies takes the form of a hard and shiny chrysalis, whereas for the vast majority of moths, it takes the form of a soft and silky cocoon.

Adult Appearance:
Perhaps the most immediately apparent way in which adult butterflies and moths are distinguishable from one another is via reference to their colouration, with butterflies typically being brighter and more colourful, and moths usually being of grey and / or brown colouration.  This is related in no small part to butterflies having evolved to select mates visually, whereas moths seek out mates using their scent receptors. 
Further physical indicators are the shape and thickness of the insects, as well as the positioning of the insects’ wings when resting. 

Butterflies, unlike moths, are able to absorb solar radiation as a means to warm their bodies and regulate their temperature.  Moths lack this ability, and warm themselves by vibrating their wings.  To compensate for their inability to absorb solar radiation, moths tend to have stout and hairy bodies, allowing them to better retain heat. 

In terms of wing positioning, butterflies usually close their wings together vertically above their thoraxes; whereas moths allow their wings to rest spread out either side of their bodies. 
One additional distinguishing physiological feature separating moths and butterflies is the form of their antennae.  Butterfly antennae are thin with bulbous club-shaped tips, compared with the fuzzy antennae of moths.
There are of course exceptions to each of the general rules set out above, and if in doubt, it is worth referring to two or more when attempting to observe and classify an insect as either a butterfly or a moth.

Summary:
In summary, one is more likely to spot butterflies during the day, and moths at night.  Butterflies are more colourful and slenderer; whereas moths are thicker, fuzzy looking and of dull colouration.  This is accentuated by the resting positions adopted by each insect, with butterflies closing their wings together vertically, and moths allowing their wings to rest at their sides.  Much like the rest of their bodies, moths’ antennae are fuzzy, unlike those of butterflies, which are slender and club shaped at the end.

Take care when setting out to observe and identify these insects.  Their beauty is matched only by their fragility, and they must be handled with great care, if at all.

Article by James Moody
29th May 2019

Swallowtail butterfly photo credit (top)  - Steve Lund

Cinnabar moth (bottom)