Butterflies: The battle of the sexes

You might have seen a flurry of colourful winged friends in your garden this summer – not with feathers, the other kind! Butterflies are out in the hundreds of thousands, and that means the Big Butterfly Count is underway, beginning on 15th July and running until 7th August 2022.

This is a national survey measuring the health of the environment by estimating the number of butterflies around the UK by species. Butterflies are crucial in helping us determine the state of the environment and its wildlife, as declines in butterfly populations can be an early indicator for other wildlife loss.

Anyone can take part in the survey (there were over 107,000 participants last year!); all you need to do is:

1. Spend 15 minutes counting butterflies. Record how many you see by species (refer to the list of target butterfly and day-flying moth species here).
2. Submit your record via the Big Butterfly Count website!

That’s all there is to it. The Butterfly Conservation have created a restricted list of butterflies and day moths to look out for in order to minimise counting errors, but you can record ones you’ve spotted outside this list on the iRecord Butterflies app. 

Why do male and female butterflies look different?

When you’re spotting butterflies, you may be able to identify different species, but remember that the male and female sexes of that species may look different. This is the case in many animals, including birds, reptiles, other insects and mammals, including humans. Even plants exhibit differences in appearance between the males and females of the species.

This is called sexual dimorphism. Differences in appearance can range from the size of the butterfly, to its colour and markings (known as dichromatism). Quite often, females are less colourful, but larger than males; however, this varies by species (for example, the male monarch butterfly is larger than the female).

Why are male butterflies more colourful than females?

When it comes to colour, there are a few reasons why females are less colourful than males. The choice of mate often lies with the female, and they may choose based on brightness and boldness of colour. It also suggested that females are less colourful as they carry eggs, and so their colour needs to be less attractive to predators.

Why are female butterflies larger than males?

Female butterflies carry their eggs, and spend time picking a safe place to lay them so that their offspring have a good chance of survival. This means that their bodies tend to be larger in order to support their eggs physically and nutritionally. As mentioned earlier, this is not the case in all butterfly species. 

Common UK butterflies and their sex differences

Common blue

 

The common blue males have vivid blue wings with a distinct white outline and grey undersides. Females have speckled brown wings with an orange crescent; depending on their location, their wings will also contain some blue (usually those found in the north and west of the UK).

 

Speckled wood

Female speckled wood butterflies are larger than their male counterparts, and have more defined cream patches on their wings – though this can be a little hard to distinguish! Males are more identifiable by their behaviour; they will often guard a sunny patch of territory, and fight off other males!

 

Brimstone

There’s an ever so slight colour difference between female and male brimstone butterflies. The wings of a female are a very pale green, almost verging on white, whereas the males have a richer yellow-green colouring on their wings.

 

Red admiral

One of the most well-known UK butterflies, the red admiral is distinctive in its appearance. Males and females appear very similar, with the size as the main difference – females are slightly larger than males, with wingspans reaching up to 7.8cm in width.

 

How to encourage butterflies into your garden

There’s a very easy way to encourage butterflies into your garden, and that’s to introduce pollinator friendly plants such as the nectar-rich Buddleja ‘Butterfly Candy’, verbena, sedum, hebe and lavender. Native hedges also make great habitats for butterflies.

 

Buddleja ‘Butterfly Candy’

 

In addition, you could place some special butterfly houses in your garden, such as this butterfly and bee box from Vivara. These provide accommodation for pollinating insects, and will encourage a healthy garden through pollination!

I created some specific British wildlife guides for the months of March, April and May in cooperation with Vivara, who are the official sponsors of this year’s Big Butterfly Count. If you need some ideas for helping local wildlife in time for next spring, have a read!

Which butterfly species have you spotted so far this month? Let me know in the comments section below.