16 May 2015

Larval Host Plant for Butterflies: The Wild Cinnamon

Butterflies' Larval Host Plants #1
The Wild Cinnamon (Cinnamomum iners)


This 1st instalment of our Butterflies'  Larval Host Plants series features a species of the family Lauraceae, Cinnamomum iners. The genus Cinnamomum comprise over 300 species in tropical and subtropical regions. Due to the presence of aromatic compounds  in leaves and barks, a number of notable Cinnamomum  species have commercial value as spices: 1) Indian bay leaf comes from the species  C. tamala; 2) camphor is derived from C. camphora; and 3) cinnamon is made from inner barks of several species including C. verum (true cinnamon)  and C. iners (the subject of this article).

C. iners is widely planted as ornamentals or as hedges in gardens and parks in Singapore, likely due to its attractive foliage when there is a growth of new leaves of red and pink,. It is native to the Malaya peninsula, Singapore and India, but can be commonly found across the tropical regions. In Singapore, besides gardens and parks, this plant can be found in secondary forests, forest edges, and wastelands.

Plant Biodata :
Family : Lauraceae
Genus : Cinnamomum
Species : iners
Synonyms : C. initidum, C. paraneuron
Country/Region of Origin : Tropical Southeast/South Asia
English Common Names : Clove Cinnamon, Wild Cinnamon
Other Local Names :  Kayu Manis, 大叶桂 , 野樟树
Larval Host for Butterfly Species: Graphium sarpedon luctatius (Common Bluebottle), Chilasa clytia clytia (Common Mime), Cheritra freja frigga (Common Imperial).

A wild cinnamon tree in the Japanese Garden. Left: without new leaf growth. Right: with new leaf growth.

An evergreen, small to medium-sized tree that grows up to 18 m tall, the Wild Cinnamon features ovate-oblong leaves ranging from 8 to 30cm long. The thin and leathery leaves are simple and 3-nerved at base (having three longitudinal veins) and are arranged in opposite pairs. New leaves appears twice or more in each year. The young leaves are initially reddish pink.

The reddish pink young leaves.

Maturing leaves as the reddish coloration fades away.

The reddish and light green young leaves showing the three longitudinal veins.

The maturing leaves are soft and drooping, and light green in colour. Fully matured leaves are stiff and dark green. Traditionally, the leaves  have medicinal uses as treatments for diarrhea, coughs, fever and rheumatism, and as an antidote for poisoning by the latex from the Poison Arrow Tree.

Drooping young/maturing leaves.

Mature leaves of the Wild Cinnamon.

Flowers of the Wild Cinnamon are small, creamy white to yellow and occur in panicles (much-branched inflorescence). These bisexual flowers attract insects such as bees, hoverflies and small beetles to act as pollinators in the reproduction process.

Panicles of flowers of the Wild Cinnamon.

Close up view of the flower buds.

Close up view of the creamy yellow flowers.

The small berry-like fruits are round to oblong, about 1.5x1 cm. They are initially green, but turn dark blue to purple when ripe.

Bunches of fruits of the Wild Cinnamon.

Left: young fruit; Right: mature fruit of the Wild Cinnamon.

In Singapore, the Wild Cinnamon also serves as the larval host plant for three butterfly species: Common Mime, Common Bluebottle and  Common Imperial. The first two are swallowtail species, while the last one is a lycaenid.

A Common Mime butterfly.

A Common Bluebottle butterfly.

A Common Imperial butterfly.

Eggs of these three butterfly species are typically laid by the mother butterfly on the stem/leaves of a young shoot of the Wild Cinnamon, usually when the plant still at the sapling stage, at low heights (knee height to chest level).

A female Common Mime butterfly laying an egg on the underside of a young leaf of the Wild Cinnamon in a wasteland just outside the Dairy Farm Nature Park.

A female Common Bluebottle butterfly laying an egg on the stem of a young shoot of the Wild Cinnamon in the Southern Ridges.

A female Common Imperial butterfly laying an egg on a young leaf of the Wild Cinnamon in the Southern Ridges.

Left: eggs of the Common Mime; Right: an egg of the Common Bluebottle, found on young shoots of the Wild Cinnamon in a western wasteland.

Caterpillars of all three species feed only on young leaves of the Wild Cinnamon, and avoid the fully mature leaves altogether. When resting between feeds, caterpillars of both Common Mime and Common Bluebottle position themselves on the upperside of the leaf, and are thus relatively easy to spot. As a lycaenid, one might expect to find caterpillars of the Common Imperial in the company of attending ants. However, this is not the case as the Common Imperial caterpillar lacks the dorsal nectary organ and tentacular organs typically found in most lycaenid species.

Two eggs and one 1st instar caterpillar of the Common Mime found on together on a young shoot of the Wild Cinnamon in Jurong Eco Garden.

A 2nd instar caterpillar of the Common Mime resting against the mid-rib on the upper surface of a young leaf of the Wild Cinnamon.

A 5th (final) instar caterpillar of the Common Mime found on a leaf of the Wild Cinnamon in the Southern Ridges.

Early instar caterpillars of the Common Bluebottle found on the upperside of young leaves of the Wild Cinnamon in the Telok Blangah Hill Park.

4th instar (left) and 5th instar (right) caterpillars of the Common Bluebottle sighted in Mount Faber.

Caterpillars of the Common Mime typically wander away from the leaves and choose a stem/branch (not necessarily on the same Wild Cinnamon plant it feeds on) as its pupation site. Common Bluebottle caterpillars, on the other hand, could simply choose to pupate on the underside of a leaf or stem of the same Wild Cinnamon plant. In the case of Common Imperial, the pupation site is usually a spot on the stem of the same plant it feeds on.

A pupa of the Common Imperial found in the Southern Ridges.

Two views of a pupa of the Common Bluebottle on the underside of a leaf of the Wild Cinnamon.

Two pupae of the Common Mime on the same branch.

So when you are out in our parks and gardens, take a closer look whenever you encounter the Wild Cinnamon, and you may be pleasantly surprised by the sight of caterpillars or pupae of these three butterfly species, or better still, the sight of a mother butterfly doing its oviposition run. 

References:
Text and Photos by Horace Tan.

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