Naturespeak A naturalist's view of the world

September 26, 2010

It Just Ain’t Natural!

Filed under: Uncategorized — wykes @ 5:11 pm

If I were to read you a headline like “Mom Gives Birth to Pregnant Daughter,” it would be natural for you to suppose that it came from the “National Enquirer”. After all, this would rank right up there with alien space babies and man-eating chinchillas in terms of un-believability, right? Well, actually, this statement could have “Scientific American” legitimacy if the mom/daughter/un-born trio in question were insects –aphids to be exact. These tiny sap-suckers can do this kind of thing, you know, and I find it to be slightly unsettling from a male’s perspective. But, there is a deeper horror to this scenario.

This summer has been an especially good year for aphids, which is why I bring this topic up. By good, of course, I mean bad for you gardeners out there.  I guess I can’t speak up for all types of aphids, but I can definitively state that this has been a banner year for a specific kind known as the Oleander Aphid (see above). A carrot-colored European immigrant who hitched a ride on imported Oleander plants, the O. A. (as I shall call the Oleander Aphids from now on) have taken to our native milkweeds in a big way. Butterfly weed, Common Milkweed, and Swamp Milkweed fall into this category. Not every plant, but a majority of those I saw after mid-summer were infested with the O.A.s. The spindly Swamp milkweed has certainly been hit hard.

A normal Swamp Milkweed in autumn should be bearing upward pointing seed pods – string bean versions of the more robust Common Milkweed pods (see here). An O.A. infested plant, on the other hand, will be nearly un-recognizable (see here a shot with a lone ladybug feasting on the flock). The creatures will populate the tender stems and leaves in such numbers that the plant is completely covered. In small numbers, the creatures do little harm, but in big numbers they can literally suck the life out their host. This is not the deeply unsettling part of my discussion, by the way, but it is bad enough.

Up close, an individual O.A. looks like an orange balloon with a pair of black bristles sticking out of the fat end.  It is exceedingly hard to just see one of these aphids, I know, but a close look at a colony will show lots of individuals. The narrow, or head end, is equipped with a hollow straw mouth which does the plant juice sucking. Those butt end bristles, called cornicles, are also hollow and they exude drops of sugary fluid called honey dew. Again, even though this sounds frighteningly close to “Honey Do” – as in jobs- I have not yet arrived at the scary part.

These creatures are flightless, for the most part. Generation upon generation will pass before a few scattered winged ones appear (see above the individual at top center). The winged alates, as they are referred by people far smarter than I, are for migration purposes.  When a colony gets so dense that their host plant starts to die from sap drainage, the winged forms are released onto the world in order to find sappy new home worlds. In truth, these distant worlds may only be a few feet away, but for a juice bag shaped wingless insect such as a typical O.A., it might as well be a million miles. So, Oleander Aphids flee the ship when times get tough.

Although not “manly”, it is perfectly alright to adopt this “rat abandon ship” mode in order to survive, but what is not alright here is that every single O.A. is a female. Yes, that’s right, every single one of these things from the tiny ones to the bloated balloon ones, and even the winged ones, are girls. There are no male O.A.s!  Yes, now you know the crux of my concern.

All aphids have the ability to reproduce by means of parthenogenesis. In other words, they can produce young without the benefit of male genetic material exchange. At the height of a season, a female can indeed give birth to a daughter who in turn is already “with egg” herself. This is called telescoping generations, by the way. Eggs are not laid, but the young are popped out just like human moms do it except without the breathing exercises (insects breathe through holes in their sides). But, even normal aphids will eventually produce a generation of males at the end of each season so that there is some sex before winter comes. Eggs are laid and the whole thing starts anew next year.

As far as anyone knows, however, Oleander Aphids never produce a male generation at all. They appear to be doing famously without the male gender – period. They are, in fact, spreading across the globe. There are other examples in the natural world where this one-sided sexism exists, but there are no examples where only males exist. I would find all this really fascinating if it didn’t trouble me to the core. The next time I feel useless I’ll have to consider the option that maybe I really am!

1 Comment »

  1. […] It Just Ain’t Natural! […]

    Pingback by Quick Links | A Blog Around The Clock — September 30, 2010 @ 10:32 am

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