In the Southwest, the aphids, or “plant lice,” comprise a number of species that come in a range of sizes (all small, from one to three sixteenths of an inch in length, according to Werner and Olson) and in a variety of colors (from green to bright yellow to black to brown). Soft and pear-shaped, the typical aphid has a distinctive pair of cornicles, or “honey tubes,” protruding from the rear of its abdomen. When called to move, perhaps due to overcrowding or declining plant forage, the aphid may dress itself in wings, which will take it to new fields.
The aphid, well represented throughout the Southwest, often gets very choosy in selecting the plant on which it will feed. A yellow and black species, for instance, lives solely on milkweeds or oleanders, said Werner and Olson. Another species may dine just on your roses or another of your garden plants. “The brown aphids that make a shiny mess under arbor vitae trees [a species of conifer] can’t even live on the related junipers,” said the authors.
In feeding, the aphid inserts its straw-like proboscis, or “bill,” through the plant skin, and sucks up the fluid, causing leaves to shrivel and, sometimes, the plant to die. Because the plant fluids lack amino acids essential to life, the aphid calls on a bacterium, which lives within specialized cells, to provide supplementary nutrients, an insect’s way of taking vitamins.
Prodigiously reproductive, the adult female aphid of the early spring may carry within her body not one, but two, generations, or a pregnant daughter—a kind of biological telescoping of the reproductive process, with no need for males. An aphid population, all female from spring into the summer, can explode almost overnight. The male aphid finally makes an appearance in the fall, as the sunlight wanes and the temperatures fall. It and the female mate. The female now produces an egg that can survive through the winter, yielding a larva that renews the aphid’s reproduction cycle come spring and summer.
Fortunately, aphids serve as a banquet for ladybird beetles and their voracious larvae as well as for parasitic wasps and aphid lions. Otherwise, aphids would soon engulf us all.
Strangely, the aphid, secreting honey dew from its cornicles, also serves as a kind of milk cow, or more aptly, a “honey cow,” for ants. DuPuy said, “Ants follow these aphids about and lap up this honey. They even have flocks of them and milk them regularly.”
By Jay W. Sharp
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