Aphids in a Savage Landscape

When aphids infest plants they tend to find a good spot to feed and then stay in one place, where they'll insert their stylets into the plant's phloem, tap its sugary sap and then settle down to reproduce. 

When you take a close look at plant surfaces you can sometimes see why these pests are more or less sedentary. Many plants, like this goosegrass Galium aparine, are covered with epidermal hairs (trichomes) that make it difficult to tiny aphids to move around.

In the case of goosegrass the hooked hairs are primarily for attaching their weak stems to supports as they grow, but those curved spines are also awkward obstacles for minute aphids to negotiate.

Aphids

Aphids, also known as greenfly, are extremely successful sap sucking insects with a phenomenal rate of reproduction, which makes them major agricultural and horticultural pests. Within a month or so the little family group of 15 individuals in the photo below have the capacity to leave many hundreds of descendants, thanks to their ability to reproduce without sex. They give birth to live parthenogenetic young, which are clones of their parent and can themselves begin to reproduce within a few days of birth.

This individual has given birth to one offspring which is already feeding on the host plant, while a second is just about to be born. These already have the developing embryos of the next generation developing inside them.

This aphid parent is giving birth while still feeding - you can see its sylets, like a hypodermic syringe, inserted into the vein of the leaf. Winged aphids like this disperse widely between crops.


Many aphids only undergo sexual reproduction as winter approaches, leaving genetically variable eggs that will include some that are better adapted to endure the rigours of winter. These well adapted survivors will hatch and clone themselves in spring.