Dark Banquet - Bill Schutt [62]
What was causing the uproar? Why had bed bugs come back with such a vengeance, and where had they been for the past fifty years or so? How were they spreading so rapidly and what could be done about them? And just what were bed bugs anyway? That seemed like a decent question to start off with.
Back in Lou’s office I continued to stare at the creatures that were now trying desperately to eat me. “Are there different species of bed bugs in here?” I asked, having noted that the insects seemed to come in several handy sizes.
“No, they’re all the same species, but you’re looking at six different developmental stages.”
I would soon learn that the smallest members of Lou’s colony were the “first instars”—newly hatched bed bug nymphs, eager for their first blood meal, and nearly invisible until they had gorged themselves.
For members of the phylum Arthropoda (which includes insects, spiders, scorpions, crabs, lobsters, and shrimp), growth presents a different set of challenges than those encountered by vertebrates like mammals. Mainly, this is because the arthropods’ hardened skeleton is located on the outside of its body. Additionally, rather than having adjoining bones articulate at specialized surfaces, their joints are actually composed of thin, highly flexible, sections of exoskeleton.
This jointed structure produces movement in its owner much like its vertebrate counterpart (with pairs of muscles working in opposition to each other)—except that in arthropods the muscles are found within the skeleton rather than outside of it.*88 Since exoskeletons don’t grow once they’ve hardened, in order for the juvenile arthropod to attain a larger body size, the entire skeleton has to be shed periodically. Ecdysis (Greek for “escape” or “slipping out of”) reoccurs at the end of specific developmental stages called instars, eventually culminating at adulthood.*89 In some arthropods (like moths and flies), the early instars (caterpillars and maggots, respectively) don’t resemble the adult stage at all. These strange-looking eating machines are referred to as larvae (or the larval stage). In other arthropods (like bed bugs and many other types of insects), the instars are called nymphs, and each successive nymphal stage more closely resembles the adult form.
The colony of Cimex lectularius I was holding in Lou Sorkin’s office contained all five nymph instars plus the adult, or reproductive, stage. Each of these developmental stages was successively larger and dependent on obtaining a blood meal that would swell a body to the point that it would burst through a suddenly ill-fitting exoskeleton. Enzymatic secretions and an increase in blood pressure also helped to split the bed bugs’ outer cuticle, which is composed of a tough waterproof polysaccharide called chitin. Littering the crevices where they hide (like outgrown clothes from Gymboree), I would come to learn that the sloughed-off skeletal casts were one of the telltale signs of a bed bug infestation.*90
Arthropods that have recently undergone ecdysis avoid predation by hiding out until their soft-shelled armor solidifies.*91
One final note about this soft-shelled phase: it’s been hypothesized that structural collapse of the arthropod body is a potential hazard for those squishy-limbed individuals who have recently emerged from a round of ecdysis. This rationale was then used to explain why the largest aquatic arthropods (like lobsters and king crabs) are far heavier than their terrestrial counterparts (crabs, insects, spiders, and centipedes).†92 Since water is more viscous than air (i.e., it’s thicker), objects in water are supported to a greater degree than they are on land (where gravity