Chalkhill blue

The chalkhill blue (Lysandra coridon) is a butterfly in the family Lycaenidae. It is a small butterfly that can be found throughout the Palearctic realm, where it occurs primarily in grasslands rich in chalk. Males have a pale blue colour, while females are brown. Both have chequered fringes around their wings.

Subspecies include:

Lysandra coridon has a wingspan of 30–36 millimetres (1.2–1.4 in). These small butterflies present a sexual dimorphism. The males having pale silvery-blue upperside of the wings with a submarginal line of grey spots on the hindwings and a thin brown and white chequered fringe. Females have dark brown upperside of wings, with marginal orange spots and also with chequered fringes. The underside of the wings show a light ochre colouration, several dark spots surrounded by white, a submarginal line of black marks, a series of marginal orange spots on the hindwings and a blue dusting near the body.

As with many blue butterflies, separation from similar species in the field is on the underside markings. Aberrations are common.

L. coridon Poda (81 c, d). male above light blue green with a silvery glitter, the black margin of the forewing broad, the hindwing with dark dots at the margin. The underside light violet-grey on the fore- wing, brownish on the hindwing, variegated with white and bearing yellowish red submarginal spots; both wings very densely ornamented with ocelli. Female above russet grey-brown, beneath earth-brown and like the male with very numerous ocelli. The area of distribution is essentially smaller than in most Blues, being apparently entirely restricted to Central and South Europe. The species occurs from England, Pommerania, and St. Petersburg southwards to Spain. Italy and Brussa, and from the Pyrenees to Orenburg. Although the species is very uniformly developed, quite a number of forms have been provided with names, being partly based on very minute differences. We deal first with the variation of the upperside. — hispana H.-Schiff. (= arragonensis Gerh.),[ now Lysandra hispana (Herrich-Schäffer, [1851])] from Spain, is paler with the distal margin more strongly spotted. — apennina[ now Lysandra apennina (Zeller, 1847 ])(81 d) is on the whole paler, the dark marginal border of the forewing being lighter in consequence of an intermixture of the ground-colour; from Italy.The Greek form graeca Ruhl-Heine is quite similar. — rezniceki Bartel, [now L. hispana var. rezniceki Bartel, 1904] from Northern Italy, is a transition to the previous; according to the description the upperside of the males is still paler. — albicans H.-Schaff. [ now Lysandra albicans (Gerhard, 1851] (81 d) is the lightest form, which is almost white above; it flies on limestone in Spain, sometimes as the only form, sometimes in the company of hispana (Ribbe). — caucasica Led. (= ossmar Gerh.) [now Lysandra caucasica (Lederer, 1870)] (81 e) extends on to the Asiatic continent, flying in Armenia and at the Black Sea. The upperside of the male is brighter blue. — In specimens from the Taurus Mts. even a slight violet sheen is present, especiallv in the outer area of the wings; this is corydonius H.-Schaff. (= olympica Led.) (81 d).[ now Lysandra caucasica (Lederer, 1870)

— The blue colour of the male may occasionally appear also in the female, being sometimes restricted to the base — ab. semibrunnea Mill. (=semi-syngrapha Tutt) — sometimes occupying the whole upperside: ab. syngrapha Kef. (= mariscolore Gerh.). (81 d). On the other hand the blue upperside of males dulled by a grey suffusion: ab. suffusa Tutt. Other accidental forms are males with red spots at the margin above: ab. suavis Schultz, and females with such spots: ab. aurantia Tutt. In ab. inaequalis Tutt the glossy blue colour forms irregular streaks on a dark ground. In ab. marginata Tutt the black margin is broadened. In ab. fowleri South the margin is white instead of black, while in ab. punctata Tutt the margins are spotted. ab. calydonius Lowe has the ground darkened and the black borders enlarged. — Equally variable as the upperside is the under surface. The ground-cqjour beneath may be very dark (especially in certain females or remarkably pale; the latter is the case in ab. pallida Tutt. The ocelli may be distorted into rays: ab. striata Tutt. Some of the ocelli may be united: ab. tiphys Esp. They may be increased in number: ab. luxurians Courv., or they may be reduced (ab. privata, unipucta, impuncta) or all be absent: ab. cinnus Hbn. {= sohni Ruhl) (81 d). More over, all these variations may be more or less slightly developed or vestigial (ab. semiaurantia, caeruleomarginata, etc), or various aberrational characters may be combined in one individual, as for instance in ab. parisiensis Gerh., which is an ab. syngrapha with the ocelli as in ab. tiphys, etc.

— Egg greenish white, with minute pale reticulation, the meshes being hexagonal. Larva bright blue-green, beneath paler, the dorsal line appearing dark owing to the dorsal vessel, accompanied by chains of yellow spots, a similar but duller row of spots above the abdominal legs. Until June on Hippocrepis, Coronilla, Astragalus. Vicia, etc. Visited by Formica flava, which is attracted by the dorsal gland. Pupa rather slender, smooth, dirty yellowish brown, with dark dorsal line and on the wing-cases pale smears, free on the ground, often under stones. The butterflies occur from June till August, being rare in some places, exceedingly abundant in others; they are everywhere found in particular localities. They have a rapid flight, which is also more sustained than in most other Blues, and go early to sleep, settling for the night with closed wings on stalks of grass or on the top of flowers while it is yet full day-light. This offers the best opportunity for collecting aberrations, since the ocelli of the underside are so clearly visible that one can pick out without difficulty and put into the cyanide bottle what one requires.

This species can be found in the Palearctic realm (western Europe, southern Europe, central Europe, Asia Minor, south Urals, and northwest Turan). The range of L. coridon occurs throughout Central Europe, and is endemic to Europe. There are a few exceptions to where it is located in Central Europe: it is not found in the countries of Ireland, Scotland, Scandinavia, the Netherlands, the Iberian Peninsula (except in its northern provinces), some Mediterranean islands (found in Corsica and Sardinia), and most of southern Italy.