We currently have this lovely male Monarch coming into our garden every day, to sup on the Zinnia flowers' nectar. You really cannot tell, at first glance, that there is anything wrong with it. Then you look harder and notice a huge piece is missing from it's right side hindwing. Almost all of that wing has gone, apart from a thin section down one side.
We have come to know it as 'our' butterfly, as it swoops and swerves around the flowers and trees, then up and over our roof, in big circles. It's with us from about 9am until 4pm and stays all day.
Should any other male Monarch stray onto its patch, it sends them away with a chase. Having said that, I noticed a bee successfully chasing it from a Zinnia flower, yesterday. The bee literally saw it off the property, before going back to the flowers, but of course the butterfly was back a few minutes later.
I found the below article explaining how a butterfly doesn't require its hindwings for flight - they are more for stability. That certainly answers my question of 'how can it fly'?
"The major part of the lift to support the butterfly's weight is generated by the flapping of the forewings. The hindwings are coupled to the forewings and mainly renders the butterfly more agile and provides increased in-flight maneuverability to escape predators.
A study conducted by Eisner and Benjamin Jantzen (in the issue of the Proceedings of the National Academy of Sciences, Hindwings are unnecessary for flight but essential for execution of normal evasive flight in Lepidoptera) proves this theory. Eisner investigated this by trimming the hindwings away bit by bit. To his surprise, he found that if he removed the entire hindwing, the insects had no problem flying. Indeed, when Eisner went on to test an extensive list of butterfly and moth species, he found that without exception they were all capable of sustained flight with only their front wings. However, he found that the linear and turning acceleration of the butterfly is compromised."
Written By: Sachin R Kamath, MSc Aerospace Engineering/ Artist/ Process & Engineering Intern at P&G
Source: Hindwings are unnecessary for flight but essential for execution of normal evasive flight in Lepidoptera
Here he is. Click on each picture below, to see a larger view.......