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The glass window - Attraction or obstruction?
Theivaprakasham Hari
[email protected]
How do I attract butterflies? How can I make butterflies come near me? This remains a frequently asked
question of every butterfly lover.
I have noticed different techniques to attract butterflies like mud-puddling, salt spreading, planting host
and nectar plants, setting up UV lighting and various baits using dead organisms, dungs, jaggery or
overripe fruits. But here in my college, we have a magical glass window that has attracted 36/138
butterflies inside the university till date. Exactly, the glass window is located on the 2nd and 3rd floor of
Academic Block II, Amrita Vishwa Vidyapeetham, Ettimadai, Coimbatore, Tamil Nadu, India. The window
acts as a butterfly magnet and helped me to document some rare butterfly species of The Western Ghats.
I was curious and often wondered, how the little-winged jewels are attracted to the glass window? The
common reason one would suggest is the blockade created by the glass on the travel path of the
butterfly. But scientifically, I find different factors playing a crucial role in this phenomenon.
Firstly, the vision of a butterfly is unique and has the widest visual range. Butterflies have a capability to
view visible spectrum along with the ultraviolet region (Image 1). To the human eye, many butterflies
appear the same, but the butterflies themselves can often identify each other quite easily using
ultraviolet markings. Similarly, butterfly use the signature of UV spectrum to detect the nectarine flowers
and the host plants. So this feature of butterfly leads to the question, Is it the UV attractive material or
coating or impurity on the glass window attracts the butterfly?
Image 1. The difference between the Human Vision, UV Vision and Butterfly Vision
Photo Credits: Dave Kennard / www.davidkennardphotography.com/ .
Secondly, I suspect the presence of three host plant namely Chloroxylon swietenia, Albizia lebbeck, and
Cassia fistula in the vicinity of the glass window that attract the butterflies . The presence of Chloroxylon
swietenia plant would have attracted the Papilio demoleus and Papilio crino; Albizia lebbeck plant -
Eurema blanda; and Cassia fistula plant - Catopsilia pomona and Catopsilia pyranthe. I have noticed the
freshly eclosed, tired female or the old aged butterflies using the glass window as a resting place. Though
the presence of host plant relates to the high probability for attraction, the reason for the attraction of
other 28 species of butterflies is still unanswered.
Thirdly, the position of the glass at an altitude 25 to 50 feet from the ground level, provides a safe haven
for the butterflies from potential predators. When butterflies rests under the leaf or branch, there high
chances of predation by birds, spiders, lizards and other organisms. And hence to escape from life
threats, butterfly may have chosen raised platforms to settle (Glass window).
Fourthly, I see the closeness of the academic block to the nearest reserve forests of Ayyasamimalai (The
Western Ghats) also as a factor to attract some rare butterfly species like Parthenos sylvia, Iraota
timoleon, and Discophora lepida. I have also noticed the resting of Tirumala limniace and Euploea core on
the glass window during the milkweed butterfly migration seasons during the months of April and
September.
PATTAMPOOCHI
A TNBS MAGAZINE
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