29 October 2017

The Butterfly Antennae

The Butterfly Antennae
A Butterfly's Antennae - Its Biological Navigation System

The curved clubbed antennae of a Common Birdwing

In telecommunications, an antenna (singular) or antennae (plural) is simply defined as an electrical device that transmits or receives electromagnetic waves through the air. The first man-made antennae was invented by German physicist Heinrich Hertz in 1888 and its development led to wireless communications across the world. In the natural world, the antennae is a pair of long, slender, segmented structures on the head of insects, centipedes, millipedes, and crustaceans. Most antennae are organs of touch, but some are sensitive to odors and other stimuli and are believed to serve the functions of smell, navigation and balance in butterflies.

A prominently clubbed antennae of a Tawny Coster

All butterflies have a pair of antennae. These appendages are connected directly to the butterfly's head and are always clubbed. The clubbed antennae are usually used in a "non-scientific" way to distinguish between butterflies and moths. In general, moths have curly, feathery, thin antennae. However, there are some moths, including some genera in the family Zygaenidae (Burnet Moths) and Castniidae (Cane Borers) that have distinctly clubbed antennae like butterflies.

The butterfly's antennae originate from the top of its head and between the eyes. These segmented antennae are known to serve different functions that aid the butterfly to smell, navigate, balance, find a mate, detect flowering plants and even tell the time of the day! The antennae is an important organ of the butterfly that, if missing or damaged, the life span of the butterfly will be severely shortened.

Butterflies don't have noses as we humans have. However, they have chemo-receptors in their antennae and legs that perform the sensory function that is equivalent of a "nose". These allow butterflies to sense flowers that are full of nectar and distinguish them from flowers that are not as productive for the butterfly to visit. The antennae's chemo-receptors that are used for assessing the environment’s physical and chemical properties also sense the pheromones of other butterflies, helping them find mates across large distances.

The butterfly's antennae are also sensitive to wind directions and changes in the velocity of the wind. This helps the butterfly ride the wind currents and maintains its way-finding ability. Near the base of the antennae, in the 2nd antennal segment, there is a special organ called Johnston's organ. This organ draws information from the antennae to help the butterfly maintain its balance and orientation during flight. This organ also helps butterflies find mates as well, recognizing the wing beats of other butterflies of the same species. Without its antennae, a butterfly may be unable to fly in a particular direction and even end up flying aimlessly in circles.

Telling the Time
Butterflies are usually active during the day, but become sedentary and stop to 'roost' when night falls. Besides using their eyes to distinguish day from night, butterflies also use their antennae as light receptors. From research done, it has been found that the antennae track the position of the sun and turn that information into a time of day. When butterflies lose their antennae, they aren't able to determine the time of the day.

A butterfly with damaged antennae will be disoriented and cannot fly properly

In a research conducted by biologist Steven Reppert of the University of Massachusetts who published a paper in Science, discovered an interesting outcome when he clipped off the antennae of the butterflies. When the butterflies lost their antennae, they no longer flew in a uniform direction. Without their antennae, the butterflies were unable to track the position of the sun. The butterflies lost the ability to navigate using the sun to ascertain the time of the day, and could no longer adjust their direction.

An important function of butterfly antennae is their ability to help the butterflies fly in the right direction. This is especially important for migratory species, such as the Monarch (Danaus plexippus). These butterflies must know the correct direction to fly during a specific season, such as flying south for the winter. This tends to work in conjunction with the clock feature; to keep flying south, for example, the antennae must determine what time it is and where the butterflies must be positioned relative to the sun's position in the sky, performing like a built-in GPS system for the butterfly.

The Lemon Emigrant has been observed to "migrate" in numbers across Singapore in one direction in the morning and then fly in the opposite direction in the afternoon

In Singapore, there have been occasions where a local species, the Lemon Emigrant (Catopsilia pomona pomona) have been seen to fly in groups across the island in a particular direction in the morning, and then fly in numbers again, in the opposite direction in the evening.

The orange-tipped antennae of a Commander

Now we know some of the functions of the butterfly's antennae. But do all the antennae look the same amongst the different species? From observations across the different species in the different families of butterflies here in Singapore, the simple answer is no. Besides being clubbed, the antennae of different families of butterflies show minor but interesting differences.

Have you noticed that the clubbed antennae of Papilionidae butterflies curve upwards?

Amongst the species of the Papilionidae, the clubbed end of the antennae for many of the species curve upwards away from the horizontal. Besides being usually jet black in colour, the clubbed end of the antennae in these Birdwings and Swallowtail species are thick and show a distinctive curve at the tip of the antennae.

But the clubbed antennae of the Danainae butterflies curve downwards?

Compare this curve with the Danainae species. Many of the Crows and Tigers' antennae also show a curve, but the curved end of the clubbed antennae usually bends downwards instead. Is there a reason for this difference between these two groups of medium to large sized butterflies?

The antennae of many Pieridae and Nymphalidae species are straight, rigid and end with simple clubbed ends

The Pieridaes' antennae tend to be short and rather straight, ending in a clubbed end without any marked curve, unlike those found in the Papilionidae and Danainae species. The same can be said of the antennae of many of the Nymphalidae species, where the antennae are straight with a simple clubbed end without any bends in the antennae. Many of these species also have a coloured clubbed tip - usually orange or yellow.

Many Lycaenidae species have banded antennae with thick clubbed ends

The Lycaenidaes' antennae have an interested banded appearance in many of the species - usually black-and-white and ending with a coloured tip. The short stubby antennae of the Curetinae (Sunbeams) are rigid and straight, usually with an orange-coloured tip. Amongst the Miletinae, some of the species' antennae end with a slight downward curve at the clubbed end.

The Hesperiidae have hooks at the ends of their clubbed antennae known as the apiculus

The Hesperiidae (Skippers) are known for their special 'hooked' feature in their clubbed antennae. This terminal 'hook', known as the apiculus, is a feature that is present in many of the Hesperiidae species where the antennae ends in a sharp tip after the club. In many species, there is usually a different colour either before the clubbed end or at the apiculus, and these may be diagnostic features of some of the sub-families of skippers. Some species also sport banded appearance on their antennae with either black-and-white or orange-and-black colours.

So the next time you go butterfly watching and are given an opportunity to study the antennae of the butterflies at close quarters, take a closer look at their antennae and note the differences amongst the different species of butterflies.

Text and Photos by Khew SK

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21 October 2017

Butterfly Photography at Our Local Parks - Bishan-Ang Mo Kio Park

Butterfly Photography at Our Local Parks
Featuring : Butterfly Habitat @ Bishan-Ang Mo Kio Park

A larger-than-life Common Tiger greets visitors to the Butterfly Habitat @ Bishan-AMK Park

I recall that, some time back in 2012, I was approached by two very enthusiastic and intelligent boys from Raffles Institution, asking for help to set up a butterfly habitat at the Bishan-Ang Mo Kio Park. At that time, the park was just newly upgraded under the Public Utilities Board's ABC programme to feature a natural stream running through the 62-Hectare park. A concrete canal was demolished and a naturalised meandering stream with lush banks of wildflowers and other water plants took its place.

The Butterfly Habitat is a narrow linear butterfly garden situated next to a paved path

Today, the park is popular with the local residents in the vicinity, and is well-utilised as an outdoor exercise amenity - complete with a dog run, cycling and jogging trails, water features, event lawns, water sensitive urban design features like bioswales and cleansing biotopes. Commercial activities like a spa and F&B outlets complete the public-friendly amenities that can be found at this park, making a weekend outing convenient and enjoyable.

A sign sponsored by April Group, describing the history of how the Butterfly Habitat @ Bishan-AMK Park started

Back to the two boys from RI - Zeng Tianchen and Ernest Aw, and their plans to set up a butterfly garden at Bishan-AMK Park. I was impressed by their systematic and organised plans to persuade the authorities to set aside a small plot of land in the sprawling park for a small butterfly garden. They crafted an entire business plan on how they envisioned the butterfly garden could work, and even scouted out for alternative sites to propose to NParks.

Ample interpretative signs help to educate interested visitors to the plants and butterflies of the Butterfly Habitat.  Signs also carry QR codes where visitors can scan and be brought to even more information on the internet.

Given my busy travelling schedule then, I was only able to spare a couple of weekends to give some advice and link them up with the parks manager of Bishan-AMK Park to get approval for the site to create the butterfly garden. They also organised a talk for the community to encourage the residents to volunteer to maintain the butterfly garden. Their enthusiasm gained momentum, and with the support of their teachers in RI and the community, the Butterfly Habitat @ Bishan-AMK Park was born.

A narrow gravel path leads the visitor into the Butterfly Habitat

NParks even organised an event and got the reputable producer of pulp and paper, April Group to sponsor an event and a series of interpretative signages at the Butterfly Habitat. Today, these signages help visitors and enthusiasts to the Butterfly Habitat to understand the plants and related butterfly species that they can find at the site. NParks also added useful educational signages to share more information about the plants that are cultivated at the Butterfly Habitat.

The Butterfly Habitat is a short linear butterfly-friendly garden, featuring many host and nectaring plants for butterflies. On a good day, one can find at least 10 species of butterflies fluttering amongst the flowers and shrubbery. A community-based team maintains the Butterfly Habitat with volunteers helping to keep the plants in healthy condition. Some of the volunteers also help to breed caterpillars and then release the adult butterflies at the Habitat.

Lush host and nectaring plants found at the Butterfly Habitat

The two talented RI boys went on to pursue their tertiary education, and the maintenance and upkeep of the Butterfly Habitat fell on the shoulders of NParks and a community of volunteers under the capable chairmanship of Tian HM, who is from the landscaping industry.

Typically, the more common urban species can be found at the Butterfly Habitat. Amongst the Papilionidae, one can regularly spot the Lime Butterfly and Common Mormon. Occasionally, the fast-flying Common Bluebottle and Tailed Jay can be observed zipping by to check out the nectaring plants.

The Plain Tiger is almost a daily feature at the Butterfly Habitat. Its caterpillar host plants the Crown Flower and Blood Flower can be found at the site, and if you look hard enough, you should be able to see some caterpillars chewing on the leaves of their host plants. Other Danainae caterpillar host plants can also be found here, and the occasional Tiger or Crow can be spotted at the Butterfly Habitat.

The Painted Jezebels visit the nectar-rich flowers at the Butterfly Habitat, and the availability of the caterpillar host plants of the Emigrant species - primarily Lemon and Mottled, ensures that these butterflies are regularly around at the Butterfly Habitat. The Common Grass Yellow makes its appearance at the Butterfly Habitat once in a while, fluttering restlessly amongst the plants, stopping to feed and then goes on its way elsewhere.

On hot sunny days, look for the Blue and Peacock Pansy butterflies. Whilst skittish, they may be approached more easily when feeding on flowers. The Tawny Coster, featured prominently on the main signage of the Butterfly Habitat, makes a seasonal appearance at the site, depending on the availability of its caterpillar host plants nearby.

Amongst the smaller Lycaenidae, keep a sharp look out for the Pea Blue, Grass Blues, Peacock Royal and other tailed beauties. The Skippers also visit the flowers and are usually more active in the early morning hours of the day. All in all, about 30-40 species of butterflies have been spotted at the Butterfly Habitat @ Bishan-AMK Park.

The planting design at the Butterfly Habitat should allow more space between the clusters of plants to avoid human-butterfly interaction that is a bit too close for comfort (for the butterflies)

The very busy park with many visitors moving around near the Butterfly Habitat does affect the butterfly activity at the site. The linear design that places the plants too close to the main footpaths tend to scare off the more skittish species as people walk or jog past.

Within the Butterfly Habitat itself, the very compact placement of plants and the narrow trails amongst the plants also reduce the opportunities for butterflies to stop and feed without being alarmed by visitors walking nearby. As the design brings human movement much too close to the plants and flowers, butterflies tend to look for "safer" areas to feed without fear of encounters with predators. Human movements are also interpreted as predatory behaviour which scares off the butterflies.

Amongst the more successful butterfly gardens, there are always open areas around the planters where the butterflies can beat a hasty retreat if any predatory movements are spotted. The design should also allow for some stand-off distance between the plants and footpaths so that the proximity of observers is outside the 'circle of fear' of many butterfly species. Otherwise the butterflies will be alarmed and fly off.

The open areas beside the stream could do with some clusters of butterfly-attracting plants in a more 'private' area for butterflies without too much human movements nearby

The area near the stream adjacent to the Butterfly Habitat should also be made use of, to create quieter sanctuaries where butterflies can feed without any disturbance from human interactions. The arrangement of butterfly-attracting host and nectaring plants should also be spread further apart and allow wider spaces in between them.

The Butterfly Habitat is not too far from the nature reserves at Lower Peirce Reservoir Park and the Central Catchment Reserves. The proximity to these nature areas should be an advantage over the more urban butterfly gardens. Hopefully, with some re-design of the planting clusters and a wider choice of plants, the Butterfly Habitat can see a greater diversity of butterfly species in future.

Text and Photos by Khew SK

Further reading : http://www.todayonline.com/singapore/bishan-ang-mo-kio-park-blossom-habitat-more-butterflies