A loveliness of ladybirds
October 22, 2015 Leave a comment
Do you know the collective noun for a group of ladybirds?
It’s a loveliness, cute isn’t it! Why do I know this?
My MSc dissertation was entitled The Mechanics of Insect Adhesion, I worked with both Asian Weaver Ants and an assortment of British ladybirds, I looked after a batch of each, a colony of Ants and a loveliness of ladybirds.
I was researching the strong adhesive forces associated with insect species, Ants are seen every day carrying objects such as leaves and twigs that are many times their own bodyweight, the very nature of the tiny beings lends them enough equivalent muscular strength per unit size to perform amazing feats of strength. But carrying these masses up vertical walls and across the underside of horizontal surfaces opens up a whole new world of incredible biological engineering
There is a famous picture of an Asian Weaver Ant suspended from a glass ceiling holding a 500mg weight between its jaws. This creature is supporting 100 times its own body weight upside down from a very smooth glass surface, the forces on its tiny feet are incredible and it was my job to look into them
I wanted to find out just how much force the ants could withstand, basing my research on previous studies from Cambridge I constructed an extremely efficient centrifuge to which I could attach discs of various materials and spin them to high rotational velocities.
I used an upside down pillar drill and a plastic box.
No really, my extremely advanced scientific equipment came from the scrap pile of the university workshop, now that’s a testament to frugal engineering.
I would take a specimen, place him on the disc and turn the drill on, slowly at first, steadily increasing the speed of rotation until the ant would detach and fly onto the protective outer casing. The whole process was videoed from above using a high speed webcam. The result, after carefully rescuing the little guy and putting him back into his enclosure, was a video of a black blur that formed a circle, I could measure the diameter of the circle at the moment of detachment (when the black blur disappeared) match that distance to the angular velocity and calculate a force of detachment.
The same process was used for the ladybirds although the blur generally had a slightly red tinge and the noise of a ladybird hitting a Perspex wall at high velocity was surprisingly louder than you may think.
I should make the important point that none of the insects were actually harmed in the making of this dissertation, part of my job was to care for the health of my specimens. I had a small loveliness that needed to be kept in good health for testing, I read as much biology as I did physics for the project, I even learnt how to sex ladybirds which is incredibly hard to an untrained eye.
Our results successfully agreed with the literature, our ants were holding on to the glass substrate at 100 times the force of their own body weight.
In an attempt to understand the physical mechanism of the adhesion we tested different glass coverings, some hydrophobic and some hydrophilic, the suggestion was that some insects would secrete a liquid to maximise the surface area of their feet in contact with the substrate, we postulated that a hydrophobic surface, one that water doesn’t stick to, would show a decrease in the adhesive potential of the animal, our results couldn’t prove such a fact but they did strongly suggest it.
Most people I share this story with assume that ants feet are the same as Gecko feet in that they adhere using tiny hairs that maximise surface area in contact with the surface, this is not true. Ants utilise small hairs on some aspects of their feet but not for adhesion, instead they have a thin fleshy pad that unfolds from between two, toe like claws that then molds itself to the surface. This pad, called the Ariola, is what makes the ants stick to surfaces.
As a relatively new graduate engineer at BSRIA I am still attempting to find an application of this knowledge to the building service industry, I’m not sure that I will achieve this goal but I will keep looking.
So there we go, a loveliness of ladybirds, how’s that for a nice thought for the day.
This article is the first in a series written by members of BSRIA’s Young Engineers Network. The author of this piece is Joe Mazzon who recently joined BSRIA as one of our Graduate Engineers. You can find out more about the Young Engineers Network on our website. If you would like to find out more about this blog series then please contact our Information Manager Jayne Sunley.