Wednesday, November 20, 2013

Dangerous-looking bug with hundreds of spines found at foot of Hougang block

Dangerous-looking bug with hundreds of spines found at foot of Hougang block
STOMPer Lau Lup spotted this dangerous-looking creature in the garden at the foot of his HDB block at Hougang Avenue 10.

According to the STOMPer, the creature was so completely covered with spines he had thought it was a cactus at first.

Lau Lup wrote:

"On Sunday, Nov 3 at about 5pm, I walked pass the garden below my block and encountered this strange and dangerous-looking insect with sharp spines surrounding its entire body.

"Initially I thought it was a cactus until the creature started crawling away from my foot.

"I quickly rushed home and brought down my camera to shoot this creature.

"I have walked past this neighborhood garden numerous times.

"This is the first time I have seen such a peculiar insect living below my block in Hougang Avenue 10.

"I wonder if this insect is poisonous?

"How does it even mate with its spines and all?

"I hope to share this creature with my fellow Singaporeans."
Dangerous-looking bug with hundreds of spines found at foot of Hougang block
STOMPer Lau Lup's unusual find

Dangerous-looking bug with hundreds of spines found at foot of Hougang block
The insect appears to be completely covered with spines

This bizarre-looking insect is the caterpillar of a species of butterfly known as the baron (Euthalia aconthea gurda).

Here are more photos of baron caterpillars.

The Common Baron (Euthalia aconthea)
(Photo by Tishfire)

The Baron
(Photo by LemonTeaYK)

This is what the adult form of the baron looks like.

The Mango Baron
The Baron
(Photos by angiud)

You can find out more about the baron in this page on the Butterfly Circle Checklist, as well as Life History of the Baron on the accompanying Butterflies of Singapore blog. Kwan of also has a gallery of photos documenting the various life stages of the baron.

Baron caterpillars feed on the leaves of mango (Mangifera indica), and as a result, this species can be common in areas where mango trees have been planted, including urban parks and gardens. Because of its diet, it is also known as the mango baron elsewhere.

Euthalia aconthea gurda caterpillar
Close-up of the head and thorax of baron caterpillar;
(Photo by depeche77)

There is no information as to whether the baron caterpillar is venomous or possesses urticating (stinging) hairs; one way to know for sure would be to allow the caterpillar's spines or hairs to make contact with exposed skin (which is generally not a recommended course of action). The baron belongs to a family of butterflies known as the Nymphalidae, and the caterpillars of some species have been blamed for stinging people, although there does not seem to be any conclusive data. It would be prudent to avoid handling any caterpillar unless you are sure of its identity and know that it does not sting.

As an aside, here is a paper that provides an excellent overview of what we know about stinging caterpillars. Symptoms are usually not life-threatening and are limited to itching and rashes, but some species are potentially dangerous, and a careless brush with one can really ruin your day.

Here are some examples of moth families with stinging caterpillars. However, most of the information as to which caterpillars are capable of stinging people is based on species found elsewhere in the world, not in Southeast Asia. The representatives of these same families in Singapore MIGHT be able to sting, although there does not seem to be much data about this at present. To make matters worse, unlike the butterflies, which are conspicuous and brightly-coloured, and are easy to observe, moths tend to be more cryptic, and hence many species have yet to be conclusively identified, nor have we been able to match the caterpillars with the (often plain-looking) adults.

Limacodidae (slug moth), Upper Seletar;
(Photo by Jacqueline)

Lasiocampidae (snout moth), Chek Jawa;
(Photo by James)

Tussock moth caterpillar
Lymantriidae (tussock moth), Singapore Botanic Gardens;
(Photo by marboed)

Most of these caterpillars seem to lose their weaponry upon developing into cocoons and subsequently emerging as moths. There are old wives' tales warning against getting too close to moths and butterflies, for fear of coming into contact with the 'powder' from their wings, which can cause blindness. However, this danger has been exaggerated; the 'powder', which actually comprises the minute scales that cover the bodies and wings of these insects, is not going to cause any serious harm. Nonetheless, it is worth noting that some moths remain capable of causing skin irritation, thanks to the retention of urticating hairs into adulthood.

Back in March 1990, several residents in Bukit Panjang suffered an outbreak of itching and rashes. This coincided with an irruption of small, brown moths that were subsequently identified as tussock moths similar to the species Arna bipunctapex (known at the time as Euproctis bipunctapex). Tests showed that the skin conditions were caused by direct contact with the adult moths. Fortunately, these symptoms subsided within a week.

Euproctis bipunctapex  - Doi Su thep, Chiang Mai
Arna bipunctapex;
(Photo by Bennyboymothman)

This episode happened in the midst of a period of hot and dry weather, which might have somehow favoured increased survival of caterpillars and pupae to maturity. Whatever the case, the result was that large numbers of these tussock moths had emerged, most likely from nearby patches of vegetation, and ended up coming into contact with people. Artificial lighting might have also been a factor in attracting moths towards residences, hence greatly increasing the likelihood of contact.

Our urban greenery provides habitat for a wide variety of insects species. Some of them are often fascinating, even downright bizarre. Yet most people hardly notice their presence, which is a shame, since observing these insects can provide excellent opportunities to expose children and adults alike to urban biodiversity, and to gain a finer appreciation for the so-called minifauna and the important roles they play in our human-dominated ecosystems.

I'm reminded of this clip from Sesame Street: