Measuring between 1mm and 1cm, aphids can be found around the world in temperate regions. This group of insects is made up of over four thousand species in ten distinct families.
They are commonly found in large groups around the stems of plants, where aphids utilise their sharp mouthpart called a stylet, piercing the plants in order to suck their sugary sap.
The practice of farming may not necessarily be an exclusively human activity.
Some species of ants and aphids have a symbiotic relationship that could be described as "farming". The "farmer" ants actively protect the aphids from predatory species, such as ladybirds and caterpillars, and are rewarded for their heroic efforts with a drop of sugar-rich honeydew, which is exuded from their aphid "cattle".
The majority of aphid species have the ability to reproduce parthenogenetically, asexual reproduction without fertilisation.
Inspired by René Antoine Ferchault de Réaumur, who could not work out how aphids reproduce, Charles Bonnet, a Swiss law student-turned-naturalist took a new born aphid and placed her in a bell-jar in 1740. After watching the aphid every day for 12 days, Bonnet made a surprising discovery - the female gave birth. This was followed over the next 3 weeks by 94 more female aphid offspring. At the time this method of reproduction was completely unheard of. Further research means we now know much more about their life cycle.
Even before they're born they have embryos developing inside their bodies. Parthenogenesis combined with this telescoping of generations give aphids an extremely rapid turnover of generations. Like tiny Russian dolls they just keep popping out smaller copies of themselves.
At the beginning of the breeding cycle in spring, females hatch from eggs and start to produce identical female copies of themselves. This process continues over the summer with some females producing over 40 generations worth of aphids, which equates to thousands of individuals. The new-born aphids also already contain the next generation, this Russian doll-like reproduction is eloquently described by Sir David Attenborough above. These wing-less females then start to produce winged females which can fly to new food sources.
In the autumn, when the daylight hours short and temperature decreases, the females begin to parthenogenetically produce sexual males and females which go on to mate. The sexual females lay eggs that overwinter starting the cycle again in spring.
Aphids are an agricultural pest and are a burden to gardeners the world over.
By removing the sap they damage the plants they feed on, decreasing growth rates and reducing yield. They can also act as a host and transmit diseases from plant to plant and the honeydew that they emit can lead to growth of damaging fungi.
Chemical insecticides are common-used commercial control, however, for some smaller lots or gardens simply spraying plants with water can be an effective control.
- In warm environments aphids can reproducing parthenogenetically for years
- Aphids have been around for 280 million years
- Some ants will protect aphid eggs by carrying them to their nests over winter