Naturespeak A naturalist's view of the world

August 27, 2007

A Snug Litttle Bug

Filed under: Uncategorized — wykes @ 8:41 pm

Milkweeds seldom fail to provide the curious naturalist with something to investigate. On this morning I stopped by the patch to see what was going on. One plant was host to a large cluster of immature Small Milkweed Bugs (that’s the species name and not just a gratuitous adjective). My attention was drawn to a singular “pup” perched on the stem apart from the others. The morning sun illuminated his gold and red body and set it aglow like a gummy worm.  This youthful bug was so thoroughly engaged in his meal that my intrusion went largely unnoticed. Fortunately I was able to capture his likeness with my camera without disrupting the peaceful scene and I left things as I found them. Take a look at my photo here.

  Such a lack of attention might have resulted in death for any other insect.  I could have been a predator and was only inches away, after all. Milkweed bugs, as it turns out, are not bothered by such petty concerns.  Along with the nutritious milkweed tissue, the glowing pup was adding the plant’s cocktail of cardiac glycosides to its own defense system. Even small Small Milkweed Bugs, have enough toxic chemicals coursing through their blood to sicken even the most persistent of attackers.  Such knowledge could lead to a laissez-faire attitude about life, but these crimson insects take life very seriously.

  As might be expected, the fact that there are Small Milkweed Bugs would insinuate that there are large ones out there as well.  Indeed that is the case.  There are several other kinds in-between. Large, small or middling, all milkweed bugs share something in common – they feed exclusively on milkweeds, are mostly red, and all suck life through a straw.

  When our little guy grows up, he’ll have a full set of half wings.  As a member of the group of insects called “True Bugs,” his order name is Hemiptera which means “half wing.”  Actually the wings are divided into a hard inner portion and a soft membranous outer portion, thus the name. An adult Small Milkweed Bug is defined by a red “X” in the middle of the back as well as a purple heart with black highlights (take a look here). By this definition, I guess this next picture could be considered X rated in that is shows several of these X-bugs mating (they join end to end for hours at a time).

  Some of you might see a resemblance to the ubiquitous Box Elder Bug, but those cousins don’t have the X pattern (they have a red chevron instead) nor are they found on milkweed.  Being in the same order as their milkweed imbibing brethren, however, they share the sucking mouthpart trait.   Out little bug pup (you might want to take another look here) was captured in the act of injecting his feeding straw, or proboscis, into the Milkweed stem.  He’s demonstrating a remarkable little mechanism.  Rather than being stiff like a drinking straw, it is extremely flexible. In detail it looks more like a dryer hose than a straw (see this micro image- look at the second picture down).  The delicate hose is protected within a two parted sheath composed of stylets.  The stylets do the actual piercing of the hard plant tissue like a drill point and create an opening for the proboscis to follow.  In the picture you can see that a portion of the stylet tube is bent back to expose the proboscis – which looks like a hair coming down from the head. What you don’t see is that the insect injects spit into the plant to predigest the tissue before sucking it up in the straw.  Kids don’t do this at home.

  Throughout its one month growth stage, the baby bug will shed its skin five times.  Each shed will increase the body and wing size until the half wing becomes a whole half (what?).  The overall red and black coloration will be constant regardless of size.  Red and black are the required dress colors for all insects that feed at the Café du Milkweed.   Milkweed beetles and Monarch butterflies share the same design as the bug. This is kinda like getting the T-shirt for your favorite restaurant, except that it basically means “Don’t eat here.”  Such a color code warns potential predators to stay away and can be considered as a public service message akin to the skull and cross bones labels on our poison jars. Eating a critter bearing the mark of the milkweed will lead to dire consequences, so don’t bother.

  Feed on little one – may the glycosides be with you. 

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