Migration and dispersal of butterflies have contrasting effect on flight morphology

August 19, 2020

Butterflies show several different types of movement. They can seasonally migrate long distances over hundreds of kilometres. Alternatively, butterflies also disperse over relatively short distances for feeding and breeding over several hours or days.

Migration and dispersal are vastly different activities with very different benefits and risks. NCBS Grad student Vaishali Bhaumik and her advisor Dr Krushnamegh Kunte decided to investigate the effects of such activities on the morphology (form and structure) and reproduction of butterflies.

To answer this research question Vaishali and her advisor decided to do field studies on several different butterfly species that displayed different dispersal and migration patterns.

The butterflies studied were: (Photos Below)In all the butterflies Vaishali and Kunte measured the relative investment into their flight muscles (flight morphology) and abdomen (reproductive tissue), as well as how many ova they kept in their body relative to their weight (egg load).

This was done using various tools and methods such as comparing the weight of different segments of their body and counting the number of ova inside of females. The results were very interesting.

The results indicated that the females of migrating milkweed butterflies undergo reproductive diapause. This means their reproductive system stops producing ova (eggs) and makes their abdomen lighter to ensure more efficient long-distance migration. This finding was in accordance with previous findings of the lab when they studied the same group.

Their results on the non-migrating butterflies (Catopsilia species) pointed towards some remarkable conclusions. Like the milkweed butterflies, the females have a much larger investment in the abdomen than males. This is because the females invest a lot of energy in reproductive tissue which makes the ova. This puts them at a disadvantage while flying by making their abdomen relatively heavier, thus requiring higher energy expenditure during flight.

The results further indicated that despite being non-migrating, the females could regulate the number of eggs in their abdomen in response to the type of movement.

Dispersing females of Catopsilia butterflies have a higher egg load than non-dispersing ones, but among dispersers, the number of ova declines rapidly as the relative size of their thorax increases.

The increase in the size of their thorax ensures that the flight muscles of the butterflies are stronger. Vaishali and Krushnamegh think that could be an adaptive response of the butterflies because they received less food as a larvae. In simple terms, when there is less food around you it makes sense to have the strength to fly longer distances to search for food and thus the give preferential investment of energy for a larger thorax (i.e. bigger flight muscles) rather than the abdomen (making eggs).

So why do the non-migrating Catopsilia butterflies have lower egg loads? Krushnamegh and Vaishali suggest that butterflies that do not disperse and stay in the same place can lay eggs frequently but in smaller batches. This keeps their bodies light and ensures efficiency during flight.

To look at the greater picture, Catopsilia butterflies are reproductively active even while dispersing, and the females carry batches of eggs as they disperse. Dispersal allows them to move from one habitat to another even if the habitats are fragmented.

However, unlike the milkweed butterflies, the Catopsilia butterflies cannot pause their reproductive activity to ensure that they can fly very long distances. With habitat loss and fragmentation becoming an ongoing global crisis, female Catopsilia butterflies carrying eggs are put under greater and greater stress. Vaishali and Krushnamegh point out that this would adversely affect the whole species as these butterflies fly over larger distances to habitats which get poorer and poorer every day.
-end-


National Centre for Biological Sciences

Related Butterflies Articles from Brightsurf:

Two centuries of Monarch butterflies show evolution of wing length
North America's beloved Monarch butterflies are known for their annual, multi-generation migrations in which individual insects can fly for thousands of miles.

Vagabonding female butterflies weigh in on reproductive strategies
A new study by researchers from the National Centre for Biological Sciences (NCBS), Bengaluru, published today in the Royal Society's journal Biology Letters, shows that dispersals, when undertaken by butterflies in search of unpredictable resources, selectively burden the egg-carrying females on their long flights.

Migration and dispersal of butterflies have contrasting effect on flight morphology
Migration and dispersal are vastly different activities with very different benefits and risks.

Scientists unravel the evolution and relationships for all European butterflies in a first
For the first time, a complete time-calibrated phylogeny for a large group of invertebrates is published for an entire continent.

Human handling stresses young monarch butterflies
People handle monarch butterflies. A lot. Every year thousands of monarch butterflies are caught, tagged and released during their fall migration by citizen scientists helping to track their movements.

What do soap bubbles and butterflies have in common?
A unique butterfly breeding experiment gave UC Berkeley researchers an opportunity to study the physical and genetic changes underlying the evolution of structural color, responsible for butterflies' iridescent purples, blues and greens.

Bacteria get free lunch with butterflies and dragonflies
Recent work from Deepa Agashe's group at NCBS has found that unlike other insects, neither butterflies nor dragonflies seem to have evolved strong mutualisms with their bacterial guests.

How some butterflies developed the ability to change their eyespot size
New insight on how a butterfly species developed the ability to adjust its wing eyespot size in response to temperature has been published today in eLife.

Butterflies can acquire new scent preferences and pass these on to their offspring
Two studies from the National University of Singapore demonstrate that insects can learn from their previous experiences and adjust their future behaviour for survival and reproduction.

Beating the heat in the living wings of butterflies
Columbia engineers and Harvard biologists discover that butterflies have specialized behaviors and wing scales to protect the living parts of their wings.

Read More: Butterflies News and Butterflies Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.