21 July 2012

Life History of the Bifid Plushblue

Life History of the Bifid Plushblue (Flos diardi capeta)

Butterfly Biodata:
Genus: Flos Doherty, 1889
Species: diardi Hewitson, 1862
Subspecies: capeta Hewiton, 1878
Wingspan of Adult Butterfly: 37-41mm
Caterpillar Local Host Plants:
Lithocarpus elegans (Fagaceae, common name: Spike Oak), Lithocarpus conocarpus (Fagaceae), Lithocarpus ewyckii (Fagaceae).

Physical Description of Adult Butterfly:
Above, the male is dark purplish blue with no border; the female is pale purplish blue with broad dark brown borders. Below, the markings are purplish brown contrasting strongly with pale brownish to whitish ground colour on the hindwing. There are red patches at the base of costa on both wings.  The hindwing has  a black tornal spot and a black marginal spot in space 2, both of which are surrounded by brassy scales which cover the marginal spaces from the tornal area to space 2. A distinguishing feature of Flos diardi  is the presence of two conjoined clavate spots (hence its common name: Bifid Plushblue) in  mid space 7. However these two spots could be separated in certain aberrated specimens. There is  a moderately long  white-tipped tail at the end of vein 2, and a minute tooth, one each at  the end of veins 1b and 3 respectively.

An upperside view of a sun-bathing female Bifid Plushblue.

Field Observations of Butterfly Behaviour:
The Bifid Plushblue is rare in Singapore and sightings of adults have been restricted to  shady forested locations or in the vicinity of its host plants within the 
central catchment reserve. The adults are strong flyers and  they typically perch with their wings closed, but in sunny weather the females have been observed to open their wings fully to sunbathe in between ovipositing runs.  

Early Stages:
Bifid Plushblue (as well as Flos fulgida and Flos anniella) was found in Singapore to be utilizing  Lithocarpus ewyckii as its larval host  about a half century ago (Morrell, 1956). Recent field studies have established that Lithocarpus elegans and Lithocarpus conocarpus are its larval host plants too. It is likely other Lithocarpus spp. or other non-Lithocarpus members of the Fagaceae family could serve the same role. Caterpillars of the Bifid Plushblue feed on young and immature leaves of the host plant, and have the habit of building shelters on a  leaf  for security and concealment. Sometimes several individuals could share the same shelter. In field observations, the caterpillars are invariably found to be attended by ants.

Host plant #1: Lithocarpus elegans.

Host plant #2: Lithocarpus conocarpus.

A female Bifid Plushblue laying eggs.

Eggs are laid singly or in  small groups of 2-3 on the petiole, stem or a leaf underside of a branchlet of the host plant. Each egg is about 0.8-0.9mm in diameter, white with a light dull  green tinge. It is shaped like a pressed bun with a slightly depressed micropylar area atop. The surface has a coarsely reticulated pattern of intersecting ridges with intersection points pointedly raised.

Two views of an egg of the Bifid Plushblue.

A sequence of 4 pictures showing the development of three eggs which hatched several hours apart.

It takes 2.5-3 days for an egg of the Bifid Plushblue to hatch. The caterpillar emerges after nibbling away sufficiently large part of the egg shell. The newly hatched shows no interest in devouring the remaining egg shell. The body  is   yellowish brown  in color and has a length of about 1.8mm. It has a rather flattened woodlouse appearance with a large semicircular prothorax, featuring a yellowish brown head and long dorso-lateral and lateral setae. There are also a fair number of very short setae on the body surface.

Two views of a newly hatched caterpillar, length: 1.8mm.

The 1st instar caterpillar feeds on surface of a young leaf leaving small holes on the leaf lamina as a result. Larval stages of the Bifid Plushblue are gregarious and a few caterpillars have been observed in the field sharing a feeding site with no animosity towards each other. Towards the end of 1st instar, pinky red patches appear on the front portion of the prothorax and the posterior abdominal segments. After 2 days of growth and reaching a length of about 2.5mm, the caterpillar moults to the next instar.

Two views of a 1st instar caterpillar, early in this stage, length: 2.3mm.

A 1st instar caterpillar, late in this stage, dormant prior to its moult,  length: 2.5mm.

A late 1st instar caterpillar in the company of an ant in the field.

The 2nd instar caterpillar features long lateral hairs and a black head. Long dorso-lateral setae are no longer present, but many short setae appear on the entire body surface. A number of narrow bands, alternating in paler and darker tones of yellowish green, run  lengthwise. The prothorax is marked by a large black patch with a leading edge in pinky red. The dorsal nectary organ (DNO), ringed in dark reddish brown,  is already visible on the 7th abdominal segment.  It is flanked on its upper edge by a  small dark reddish patch, and on its lower edge, a much larger one which covers the dorsum of the 8th abdominal segment. The pair of tentacular organs on the 8th abdominal segments are also present. A large black anal plate dominates the remaining posterior segments. This instar lasts for 2-3 days with the body length reaching about 4mm before the moult to the 3rd instar.

Two views of a newly moulted 2nd instar caterpillar.

Two views of a 2nd instar caterpillar, early in this stage, length: 2.5mm.

2nd instar caterpillar, late in this stage, dormant prior to its moult, length: 4mm.

The 3rd instar caterpillar resembles the 2nd instar caterpillar closely. . The DNO is now rather prominent with a broad dark brown oval ring  marking its outer boundary. The red dorsal patch on the 8th abdominal segment now has two lateral arms, though faint in appearance, reaching up to the tentacular organs. The 3rd instar takes about 3-4 days to complete with the body length reaching about 7mm.

Two  3rd instar caterpillars with the one on the left newly moulted.

Two views of a 3rd instar caterpillar, early in this stage, length: 4.9mm.

Two views of a 3rd instar caterpillar, late in this stage, length: 7mm.

Two 3rd instar caterpillars attended by ants.

The 4th instar caterpillar has similar markings as the 3rd instar caterpillar. One notable change is in the prothoracic dark patch which now has two small white markings embedded at its posterior edge. Another change is in the red side arms on the 8th abdominal segment, being longer and more prominent. The dorsal band becomes darker and prominent in this instar too. The 4th instar takes about 4-5 days to complete with the body length reaching about 12mm.

Two views of a newly moulted 4th instar caterpillar, length: 6.5mm.

Two views of a 4th instar caterpillar, late in this stage, length: 12mm.

Top: Dormant 4th intar catepillar prior to its moult. Bottom: Newly moulted 5th instar caterpillar.

Compared to the 4th instar, the 5th instar caterpillar has similar but more striking markings. Visible changes are 1) The  dark prothorax patch is now flanked in white  on its side and nearly  all its anterior edge; 2) The black anal plate is flanked in white on its side.

Ants attending to a Bifid Plushblue caterpillar while the moult to the 5th instar was in progress.

Two views of a 5th intar caterpillar, early in this stage, length: 14.5mm.

Two views of a  5th intar caterpillar, late in this stage, legnth: 20.5mm.

After 6-8 days of feeding and reaching a length of about 23mm, the caterpillar stops food intake for about 1 day. During this time, its body gradually shortens and the longitudinal bands on its body disappear. Soon the caterpillar becomes an immobile pre-pupa confined to  its leaf shelter. The pre-pupal caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches via claspers at its posterior segment. The silk threads spun is lemon yellow to golden yellow in colour.

Two views of a pre-pupa of the Bifid Plushblue.

After 1 day as a pre-pupa, pupation takes place. The pupa, with a length of 14-15mm, has a shape typical of any Lycaenid species and has a somewhat produced anal segment. It is pale yellowish green initially, but within a day, the colour changes to golden brown.

Two views of an early pupa of the Bifid Plushblue.

Two views of a pupa of the Bifid Plushblue, length:12mm.

9 to 10 days later, the pupa turns dark brown to black in its wing pads, the thorax and the dorsum of its abdomen. The next morning, the pupal stage comes to an end with the emergence of the adult butterfly.

Two views of a mature pupa of the Bifid Plushblue.

A newly eclosed Bifid Plushblue waiting for its wings to be fully firmed up.

Unlike most of the Lycaenidae species, the caterpillars of the Bifid Plushblue have the habit of constructing leaf shelters in which they rest and seek safety between feeds on the lamina of nearby leaves and part of the shelter. Pupation also takes place within a leaf shelter.

A leaf shelter  used by Bifid Plushblue caterpllars on L. conocarpus, constructed by binding the opposite edges near the leaf base.

A leaf shelter on a young leaf of L. elegans.

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
  • A Field Guide to the Butterflies of Singapore, Khew S K, Ink on Paper Comm. Pte. Ltd., 2010.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 1st Edition, 2006.
  • Notes on the life histories of a number of butterflies of the subfamily Theclinae (Lycaenidae), Morrell R.,  Malay. Nat. J. 10: 104-108, 1956.
Text by Horace Tan, Photos by Nelson Ong, Federick Ho and Horace Tan.