Butterfly and Bee Garden

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Two Common Blue Butterfly on plant

Exploring the Enchanting World of the Common Blue Butterfly

This bright blue butterfly can be found throughout the summer months in sunny and grassy areas. The common blue butterfly is small, it’s most active between April and October and it’s one of the most widespread blue butterfly species. The most popular habitats are grassy meadows, large gardens, parks, heath-land, waste ground, and woodland rides.


The caterpillars feed on rest harrow, common bird’s-foot trefoil, various clovers, and other related flora. We will take a closer look at this butterfly and how you can help to conserve this species.


1. The Common Blue Butterfly: An Overview



Common Blue butterfly with its wings closedThis butterfly is sometimes referred to as the European common blue (Polyommatus icarus). It’s part of the Lycaendae family and more specifically the subfamily which is Polyommatinae. This species is found in the Palearctic and it’s found throughout North America.

Like most butterflies, the caterpillar eats leaves to put on weight for the pupae stage after it emerges from the egg. Adults feed on wildflower nectar (which sounds divine) and excrement (which does not). Males are seen more often, they are territorial and they will deter rivals as they look for the more reclusive females.


The male common blue butterfly has bright blue wings with a white fringe and brown border. The female has a dissipated light blue tone on the body and orange spots under the hindwings, but it’s primarily brown in color. This butterfly lacks the chequered pattern found on the Adonis blue. It’s not as bright as the chalk-hill blue and it’s smaller than the large blue (which is rare). A common blue will go through four stages of life and an adult can live for up to three weeks.


Let’s take a look at Common Blue Butterfly stages of Life:


  • The Egg Stage (approximately 8 days): The eggs look like small white flattened spheres, they are 0.60mm in size, and on careful inspection, the egg sac is pale green-grey. The eggs are laid individually on the fresh sprouting shoots of one of their preferred food plants.
  • The Larvae Stage (approximately 1-2 weeks): The emerging larvae (caterpillar) feed on the underside of the leaf, which causes blotching on the leaf surface. The common blue is attractive for ants of the genera Formica, Myrmica, Lasius, and Plagiolepissi. Throughout this stage, the caterpillar will eat voraciously to prepare for the pupae stage.
  • The Pupae Stage (approximately 2 weeks): The caterpillar forms an olive green/brown chrysalis with silk strands on the base of their food plant. This would seem to be risky, the chrysalis is at ground level, but the aforementioned ants protect it from predators. The ants may take the chrysalis into their nest, or they may bury it and guard it at the site. The reason for this is that the larvae secrete honeydew which the ants like to eat throughout this stage. In scientific terms, this is described as facultatively mutualistic, and it’s a clever defence mechanism.
  • The Adult Stage (up to 3 weeks): In order to attract a female, the male is much bluer and easier to spot than the female with her darker brown upper wings. The male can fly longer distances to find a territory that has fertile females to mate with. In comparison, the female tends to fly lower to the ground as she searches for nectar to eat and good places to lay her eggs later.


2. The Secret Life of a Common Blue Butterfly


Common Blue Butterfly with open wingsThe males stake out their territory, they choose a place with plenty of flowers to attract females, and they perch in a prominent spot to defend this area. The rivals will dart at each other to chase each other and drive them away from the territory.


This aerial is spectacular, and it demonstrates the prowess of the male to protect their area. This display of aggression ends when a female arrives in the territory. The male will dote on her, and a mating dance with a release of pheromones will leave the female in no doubt that the male is interested.


The pheromones trigger the instincts of the female to mate and this courtship dance may last for several hours. The male and female may touch wings as they fly around each other. The female will allow the male to place his antennae on her wings if she consents to mating.


This is a captivating and almost romantic prequel to mating that is fascinating to observe up close. But, mating is not guaranteed, the advances may be refused, and in this case, the courtship will end immediately.


3. Threats and Conservation Efforts


The common blue butterfly was found throughout Europe and Asia, and it was widely distributed in the UK. This butterfly can tolerate a wide range of habitats, but there has been a 74% population loss that began in 1901.


This may be caused by a loss of 47% of Bird’s-foot trefoil (Lotus cornicaluatus) which is their preferred host plant. This plant is important because it nourishes the larvae after hatching from the egg, and adults can feed on the nectar-rich yellow flowers.


Common Blue sitting on flowerAt this time, the species faces two main threats: agriculture and urban development. Modern large-scale farming can destroy the common blue habitats, and the continued use of pesticides is dangerous. A great deal of our meadows, parks, and nature reserves are falling prey to urban development as cities grow. A projected rise in global temperatures may disrupt the hibernation and reproductive cycles, which could further lower the population numbers.


4. How to Attract Common Blue Butterflies to Your Garden


The first thing common blue butterflies are looking for are plants that they and their offspring can eat. Adding bird’s foot trefoil, rest-harrow, and clover species to your garden is a significant draw.

If you see a blue butterfly, look at the underside, if it’s brown with white, black, and orange markings you’re looking at a common blue butterfly. But, if the underside of the wing is pale blue with black patches you’re looking at a close relative, the holly blue butterfly.

The butterflies are more likely to take up residence if you offer them some places to shelter, such as rock pile cracks, ornamental grass, shrubbery, and more. For a small delicate butterfly, a raindrop will feel like a heavy object, and they can be injured. It’s a great idea to offer some animal dung (if you have it) or mud puddles to provide access to vital salts and minerals that the butterflies need.


Conclusion: Common Blue Butterfly


The common blue butterfly is a fascinating insect to observe and it’s an excellent pollinator for your garden. Sadly, their numbers have declined significantly, and we can all take action to help reverse this trend. Taking action in your own garden is a great start, and you can spread the word to the neighborhood. Creating a butterfly-friendly habitat is fun, but it’s even more fun when you share the experience with others. If you want to take things further, investigate citizen science projects and conservation groups working in your area.


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