Butterfly vs. Moth: What is the Difference?


The Eight Spotted Forester (Alypia octomaculata) is colourful and flies during the day. These traits make it tricky to identify as a moth.

Butterflies and moths are very closely-related insect groups that make up the Order Lepidoptera. They all use tiny coloured scales to colour and pattern their bodies and wings, and have very similar body plans and life cycles. So, what is the difference? How do you tell them apart?

How are Butterflies Related to Moths?

 

It is easiest to understand how butterflies and moths are related if you first forget the word “butterfly” altogether! Imagine the Order Lepidoptera as the “Order of Moths”. This is fairly close to reality, since moths make up nearly all species in the Lepidoptera. Now imagine that this “Order of Moths” was broken up into different groups of related moths that shared common features – like gall moths, ghost moths, leafroller moths, owlet moths, snout moths, geometer moths, big moths, small moths, fat moths, thin moths – you get the idea. Then imagine that one of these groups (just one of them!) contained “moths” that were usually brightly coloured, usually day-flying, had clubbed antennae, and pupated in a chrysalis. What would you call this group? The answer is: butterflies!

Butterflies are essentially just a very specialized group of day-flying moths,
and they make up only a tiny part of the Lepidoptera.

Conversely, the word “moth” just refers to everything that is not a butterfly. As such, moths and butterflies are very closely connected, more so than most people realize. In fact, if butterflies had just been discovered today, scientists would very likely call them moths too, and the word “butterfly” would never even exist!


How Do You Tell Moths and Butterflies Apart?


Antennae are the most reliable way to distinguish butterflies from moths. Top: Monarch Butterfly (Danaus plexippus), Bottom: Polyphemus moth (Antheraea polyphemus).

The most reliable way to tell butterflies apart
from moths is to look at their antennae.

The antennae, or feelers, are found on the head just above the eyes. Generally, butterfly antennae are ‘clubbed’, meaning that they are long and thin in the middle but end in a thicker lump, kind of like a golf club. The antennae are not fuzzy or feathery, but look more like wire. Butterflies hold their antennae out and forward, where they are easy to see.

In contrast, moth antennae tend to be thicker in the middle and get thinner towards the ends, appearing to taper to a point. Moth antennae are feather-like, covered in projections or teeth that make them look like a feather or comb. For some moths this is very obvious, but for others the feathery parts are very short and hard to see. Unlike butterflies, some moths tuck their antennae alongside their bodies when they are resting, but many hold their antennae out like butterflies do.

There are various other general “rules” for telling moths and butterflies apart, but be warned – there are many exceptions to some of these “rules,” and they are not as reliable as looking at the antennae!

Butterflies:

  • Butterflies tend to be colourful
  • Butterflies tend to be diurnal (active during the day), where the daylight makes their colours showy
  • Butterflies tend to pupate in a hard chrysalis
  • Butterflies tend to rest with their wings closed and directly over their backs (unless they are sunning)
  • Butterflies tend to have thinner bodies which are not overly fuzzy.

Moths

  • Moths tend to be drably coloured, often in browns, greys, and pale colours
  • Moths tend to be nocturnal (active during the night), where low light levels mean that only pale colours show up well
  • Moths tend to pupate inside a cocoon, which they spin out of silk
    and sometimes nearby materials like leaves
  • Moths tend to rest with their wings open or flat against their backs
  • Moths tend to have fatter, stockier bodies, and are often noticeably fuzzy

Challenge: Do you see Butterflies, Moths, or Both?



The Answer is: BOTH!

One of the reasons that the general rules aren't reliable is that some butterflies and moths break them – for example, some moths are very brightly coloured like these Sunset Moths (Urania leilus) from the family Uraniidae. Although Sunset Moths look like butterflies to the naked eye, examination under a magnifying glass would reveal that their antennae are feathered like all other moths (not wirelike and clubbed like the butterflies).