Butterflies of Northumberland

 

Featured image: Common Blue ([1] @Neil Freeman)

• Class: Insecta
• Order: Lepidoptera
• Family: Lycaenidae
• Subfamily: Polyommatinae
• Genus: Polyommatus
• Species: Icarus

 

Conservation status: Not threatened but in a slight decline.

 

 

Appearance:

• Wingspan: 29-36mm [1]
• Sexual dimorphism: Yes
• Wing Shape: Long, smooth and curved edges.
• Male Dorsal Wing: Radiant blue with a white fringe.
• Female Dorsal Wing: Fade from blue at the base to brown as the wing progresses ending in a white fringe. Highly variable amount of blue [1].
• Male Ventral Wing: Brown base colour with splattering of black spots with a white surrounding before a line of definitive orange spots. Males have more of a bluish tint at the base of the wing.
• Female Ventral Wing : Brown base colour with splattering of black spots white a white surrounding before a line of definitive orange spots.
• Body: Blue/brown with whiter legs.

The females are not as radiant as the males. The wings fade from blue to brown and end in a white fringe. Female Common blues are very similar to the Brown Argus and Northern Brown Argus butterflies. Common Blue are distinguishable due to the blue shine at the base of the wings on the dorsal side. The amount of blue colouration is highly variable and is more distinguishable further north [3].

Distribution:

The Common Blue is Britain’s and Europe’s most widespread blue butterfly [1,3]. It is very common in a range of habitats in particular grasslands, woodland and sheltered sunny areas[1,5]. The butterflies range within the United Kingdom is one of the largest, ranging from the very Northern Tip of Scotland right down to the South Coast of England [1,4,5}.

The Common Blue has also recently been discovered in North America where it is increasing in numbers [5].

Life Cycle:

The Common Blue butterfly undergoes two broods each year. In more Northern populations it is more common for there to be only one brood each year [1,2,4]. The larval food plant is most commonly the Birds-Foot Trefoil (Lotus corniculatus) [3,6]

Butterfly: Two brooding butterflies emerge in early May where they reach their peak before mating and dying [1,6]. The next generation of adult butterflies then emerge during late July, peaking in August [1,6]. For more Northern individuals, (above Derbyshire [4]) The single brood strategy is adopted. The adult butterflies emerge in June and peak in July [1].

Egg: Eggs are laid in June and then August/September. The eggs are laid individually on the leaf surface of their food plant. Each egg is white in the shape of a bun, the eggs are not camouflaged and hatch into the caterpillar within a week [1].

Caterpillar: The hatched Common blue caterpillars are short, green, furry and hibernate throughout winter amongst the leaf litter on the floor [1]. Caterpillars feed upon the underside of the leaves leaving behind distinctive silvery blotches on the leaf surface that are visible from above [1,6]. the caterpillar has an attraction for ants as it secretes a sugary substance which the ants uses to gather nutrients in exchange for protection from predators [2].  In Southern two broods, the first generation does not hibernate and in which case the pupal stage only last 2 weeks [1,6].

Pupa: The pupa is formed on the ground or at the base of the foodplant [1]. This stage lasts for up to 2 weeks and in some cases ants will carry the pupa and bury it in the ground [1].

Behaviour:

Common blue butterflies enjoy the sunshine and are seen at their most active during warm sunny days [1]. The males are more active and females more secretive as they visit flowers and nectar [1]. Common food sources are Birds Foot trefoil, buttercup, daisy, milkwort, bugle, thistles [1,6].

Common blues spend a long amount of time basking in the sun with their wings held half open [6]. Males and females tend to roost on long grass facing downwards often in groups of 4-5. Roosting above the floor keeps the butterflies safe and away from potential predators such as mice [6]. The males tend to rest in prominent positions where they can be in sight of females and no such courtship rituals take place before copulation [6].

Common Blue butterflies in Northumberland:

North East England Status: Common Resident [7]

The Common blue is a butterfly that is likely to be discovered within Northumberland. The males are easily distinguishable by their radiant blue colouring but the females however are quite similar to the Brown Argus. Slight differences in the blue tinge on the dorsal wing allow for distinguishing this species. Also in Northumberland the Brown Argus is very rare so in most cases, trouble in distinguishing between the two it is more likely to be a female Common Blue.

The Common Blue is a frequent butterfly found along the coast as well as in land areas where there is an abundance of Birds-Foot trefoil [8]. There is an absence of Common Blues in intensive farmland due to the removal of Birds-Foot Trefoil [8].

3373 individual common blues were recorded in 2015 across Northumberland [9]. The Common Blue continues to be very widespread and common however numbers have been falling since 2011 [9].

 

References:

[1] -UK Butterflies (2017) Common Blue http://www.ukbutterflies.co.uk/species.php?species=icarus Accessed 2 Feb 2017.

[2] – RSPB Royal Society for the Protection of Birds (2017) Common Blue http://www.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/a-z-of-a-wildlife-garden/atoz/c/commonbluebutterfly.aspx Accessed 2 Feb 2017

[3] – Butterfly Conservation (2017) Common Blue http://butterfly-conservation.org/50-1176/common-blue.html Accessed 2 Feb 2017

[4] – British Butterflies (2017) The Common Blue https://www.britishbutterflies.co.uk/species-info.asp?vernacular=Common%20Blue Accessed 2 Feb 2017

[5] – Wikipedia (2017) Common Blue https://en.wikipedia.org/wiki/Common_blue Accessed 2 Feb 2017

[6] – Learn About Butterflies (2017) Common Blue http://www.learnaboutbutterflies.com/Britain%20-%20Polyommatus%20icarus.htm Accessed Jan 31 2017

[7] – North East Butterflies (2017) Butterfly species. http://www.northeast-butterflies.org.uk/speciesb/butterflies.html Accessed 2 Feb 2017

[8] Cook NJ (1990) An atlas of the butterflies of Northumberland and Durham. Northumberland biological records centre, the Hancock museum. Newcastle Upon Tyne

[9] Fleming S, Waller I, Perkins M, Norman R, Dover, Donnelly A (2015) Butterfly summary 2015. Northeast England branch. Butterfly Conservation. http://www.northeast-butterflies.org.uk/download_files/2015ButterflyReport.pdf Accessed 25 February 2017