11 May 2008

Life History of Eetion elia

Life History of the White Spot Palmer (Eetion elia)


Butterfly Biodata:
Genus: Eetion de Nicéville, 1895
Species: elia Hewitson, 1866
Wingspan of Adult Butterfly: 38mm
Caterpillar Host Plants:
Cleistanthus sumatranus (tentative, to be confirmed)

Physical Description of Adult Butterfly:
Above, the wings are dark brown with the forewing possessing separated white hyaline spots in the cell and in spaces 1b, 2, 3, 4 and 5 (two minute spots), and with sub-apical spots in spaces 6 to 8. On the hindwing upperside, there are spots in spaces 1b, 2, 3 and conjoined spots in spaces 4 and 5. The hindwing underside has the basal half silvery white below vein 8. The abdomen is dark brown, white banded above and entirely white beneath. On the upperside of the forewing, the male has a narrow arcuate whitish brand from just below vein 2 to before the origin of vein 3.



A view of the upperside of a male Eetia elia showing its brand

Field Observations of Butterfly Behaviour:
This species is rarely encountered in Singapore. Past sighting locations of the adults include various parts of the Central Catchment Area such as MacRitchie Nature Trail, Sime Forest and Upper Seletar Reservoir Park. As typical with other skippers, the adults fly with swift and darting flights.

Early Stages:


Host plant

The eggs are laid singly on the leaf upperside of the host plant. Each egg is mostly pink and has a darker shade of pink at the micropylar area. It is spherical with a flattened base and has a surface covered with a fine mesh of short wavy lines. The diameter is about 0.9mm.


Two views of an egg of Eetia elia


Mature egg with a faint view of the head (left), empty egg shell (right)

It takes 3 days for the collected egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 2.5mm. It has the typical cylindrical shape for skipper caterpillars, and a large black head. The body colour of the 1st instar could range from yellow to orange as depicted below.


1st instar caterpillar, length: 2.5mm

After a quick exit and look around, the young caterpillar returns to the remnant of the egg shell to munch away more of the egg shell for its first meal. It does not finish the entire egg shell and soon makes its way to the leaf edge to construct its first leaf shelter. It rests within the shelter and ventures out to eat the leaf surface nearby and parts of the shelter. With additional cuts to the leaf flap and further silk threading work, the shelters for the first instar (and second instar) caterpillars soon assume a convex and tent-like appearance.


1st instar caterpillar, 4mm


The tent-like leaf shelter for a late 1st instar caterpillar.

As with some other skipper species, Eetion elia caterpillars have been observed to ballistically eject their faecal pellets (frass) at speed, ensuring that the pellets are displaced as far away as possible from the shelter. This is believed to be a self-defense strategy, preventing potential predators or parasitoids from following the chemical signature of the frass to the originator.


2nd instar caterpillar, early in this stage, length: 7mm

After 3 days in 1st instar and reaching a length of about 5mm, the caterpillar moults to the next instar within the shelter. The 2nd instar caterpillar is yellow with a green undertone. It reaches a length of about 9mm after 3 days of growth in this instar. The 3rd instar caterpillar has similar appearance as in the previous instar. As it grows, the body takes on bands of transverse ring patterns alternated with bands of smooth skin. The 3rd instar lasts about 5 days with the body length reaches 14-15mm. The leaf shelters for the larger caterpillars in 3rd and later instars are made from bringing two edges of the leaf together with sinuous cuts and silk threads, resulting in a ``curry puff'' appearance. The caterpillars eat the leaf adjacent to the shelter as well as the edges of the shelter.


3rd instar caterpillar, early in this stage, length: 9mm


3rd instar caterpillar, late in this stage, length: 15mm


Leaf shelter for a 3rd instar caterpillar over a 2-day period.

The 4th instar caterpillar has a rather different looking head capsule. There are three large and dark brown spots set among a light brown base colour. This instar takes about 5 days to complete with the body length reaching 23-24mm.



4th instar caterpillar


5th instar caterpillar, early in this stage, 26mm

The head capsule of the final and 5th instar caterpillar has an orange base color, and has all three black spots well defined and set within rings of beige coloration. This stage takes about 9-10 days to complete with the body length reaching 40mm.



5th instar caterpillar, late in this stage, length: 40mm

At the end of 5th instar, the body of the caterpillar shrinks in length. Soon it becomes dormant in its leaf shelter and enters the prepupatory phase which lasts for one day.


Pre-pupatory larva of Eetion elia

Pupation takes place within the leaf shelter. The pupa secures itself with its cremaster attached to a short transverse band on the leaf surface, and has a silk girdle. The pupa is mostly pale green in base colour. It has a short thorax, a rather long abdomen, a long and pointed rostrum. There is also a pair of small but distinct orange-brown patches on the anterior part of the mesothorax. Length of pupae: 30-34mm.


Fresh pupa of Eetion elia

After 9 days, the pupa becomes mostly black in color with spots on the forewing upperside visible through the now transparent skin. Eclosion takes place the next day.


Mature pupa of Eetion elia



A newly eclosed Eetion elia


Another newly eclosed Eetion elia

References:

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
  • The Butterflies of Hong Kong, M. Bascombe, G. Johnston, F. Bascombe, Princeton University Pres 1999



Text and Photos by Horace Tan

3 comments:

EUNICEEESH(: said...

Hi,

Would you mind helping me ID a caterpillar? The picture of the cat can be found @ http://naturallyours.blogspot.com/2008/05/18-tree-with-lots-of-caterpillars.html (which is my blog). Thanks a bunch!

Horace said...

The caterpillars and pupa shown on your blog page should be the early stages of Painted Jezebel (Delias hyparete metareta). For more info and the picture of the adult butterflies, you could refer to the page at http://www.sgbug.org/butterflies/spc_info.php?spc_id=15

EUNICEEESH(: said...

Thanks alot~!