Potty Gardening Club: Ant Farmers and Aphid Cattle
Some of the smallest creatures in your garden are the insects and they are truly wonderful and fascinating little beasties. A garden may contain hundreds of unseen insects all trying to multiply and survive in whatever way they can and some insects have ingenious ways to help them survive. One of the most abundant insects in your garden are Aphids. Both Blackfly and Green fly are aphids, sap sucking insects common on both outdoor and indoor plants. If you look on some bushes or trees you may see them under the leaves and on the stems, there could be thousands of them depending on the size of the plant and they are all sucking the sap from the stems. This does not do the plant any good at all – in fact plants can die through over infestation of Aphids.
It is estimated that a mature tree can host around 2.5 million aphids and they multiply quickly. The females reproduce through parthenogenesis, which means the eggs don’t need to be fertilised by a male. A solitary greenfly can produce 80 or more offspring within its short lifespan. Each offspring is able to lay eggs as soon as they are hatched, which takes about a week. It’s mind boggling to try and work out the numbers. Many Gardeners spray insecticide to control Aphids because of the damage they do to plants, but aphids aren’t all bad.
Aphids provide food for Hoverflies, Lacewings and Ladybirds including the lady bird larva – a ferocious hunter (See pictures below).
The poor Aphid has no defence against these predators, but all is not lost as Aphids have an ally. Black fly and Green fly live off the sweet sugary sap of the plants they infest. They digest this and secrete a substance called honeydew. This sticky secretion is a favourite food of ants, who domesticate the aphids like we do cattle. Ants actually “milk” the aphids by stroking their abdomen encouraging the secretion of honeydew. Both the aphids and the ants benefit from this symbiotic relationship – the Aphids provide honeydew and in return the ants protect the aphids from predators such as lacewings and ladybirds, savagely attacking and overwhelming them, killing them or throwing them off the plant.
It has also recently been found that the ants will protect the aphids from fungal outbreaks by removing the bodies of the infected aphids and disposing of them. Next time you see a lot of ants on bushes and trees it may be because they are farming Greenfly, you could take a careful look but beware some ants may bite or spray stinging acid in an attempt to protect them. Have a look at the pictures of Ants farming Blackfly in my garden. I was lucky enough to have a Hoverfly arrive for lunch as I took the photos.
Until next time,
Written by Rob Gagliano, Casual Learning Development Leader and Natural Science Collections Volunteer