ON DOG TICKS,l

Ticks can smell!

The tick season has arrived.  Those tiny, flat, brown, arachnids are on the prowl again.  These blood sucking little critters are dangerous.  They complete their life cycle only by burying their head in your skin (or your pet’s skin)  and gorging bloob like a vampire. In the process they said well up to three or four times their original volume. .  Whereupon finally blown up to look like a shiny bead-pearl they fall off The host and begin their life cycle again.    In their passage through their blood sucking life they often pick up a host of deadly diseases which they can pass on to their human hosts:.Lyme, Babisiosis, Erlichiosis, Rocky Mountain Spotted Fever, etc etc.

These eight-legged members of the spider “family” live among the weeds, brush and waste places around every home. Over the millions of years of evolution they  have evolved a very efficient system to help them find hosts and complete their bloody life cycle.  They can smell!

  Yes these tiny arachnids can smell you out.  Their olfactory organ is not located on the front of their head—their “nose”. No, that part of the head, where a nose would be is instead devoted to blood sucking.  (This critical part—the probosis—is composed of a central straw/like tube bounded on each side by a sharp pointed harpoon-like appendage armed with rear-projecting barbs.  These “side harpoons” slide forward and backward on either side of the central “sipper” tube,  In the process of entering the skin of a host these harpoons  move alternately as they drive the proboscis deeper into the host’s  skin, eventually  positioning  the “sipper tube” deeper and deeper through the epidermis into a region where it can draw blood.

The twin harpoons with their array of rear facing hooks,  once deeply embedded, make it near impossible for the tick to pull out if it wanted to or to remove the critter without tearing off the  elaborately armed “nose” or “probosis”.  On removal this part —the tube and harpoons are most often left behind embedded in the host’s skin to fester there when the tick is pulled out. )

So with its “nose” area devoted to harpooning a host and sucking blood, any olfactory organ (“smeller”) had to be located elsewhere.  In the tick anatomy, that elsewhere is on the “wrists” of their most anterior appendages or front legs.  These tiny “smelling” organs known as Haller’s Organ are comprised of a tiny pit on each “wrist” of the first appendage.  The pit is lined with sensory setae (hairs) which seem to be able to sense the presence of carbon dioxide gas, ammonia, and other mammalian generated chemical vapors.  Some claim they may also sense heat.

Thus a tick can “smell out” its host.  When  a cat or dog—or other warm blooded animal—passes through a brushy area.  As it moves through this environment it leaves behind a trail of CO2 gas, as well as a gaseous trail  of organic molecules resulting from the animal’s metabolic processes, such as carbon dioxide, urea, ammonia etc. etc.  Ticks In the surrounding area respond and can home in on these scents using their Haller Organs to direct them.  By always moving toward  the more concentrated  scent they eventually crawl up onto the branches or leaves which were in contact with the passing host animal.   There they lay in wait.

In a tick’s view, if an animal had passed this way once...it is likely it will return.  The ticks  position themselves in a near upright stance ,  with their hind appendages holdong on to the leaf or branch and their fore appendages (these are armed with entangling bristles) are extended outward ready to engage the fur or fabric of a passing host.  When a tick  senses the approach of a host (perhaps by sensing heat) they simply extend their appendages and are literally swept up onto the skin or fur of the potential host.

Once aboard a host animal  they cling on tightly and begin to move upward.  Ticks are antigeotropic. They sense gravity and move opposite to its attraction —upward.  They will not turn to go down.  Thus a downturned  collar on a long sleeved shirt  will protect a human host from ticks crawling over its neck and into his or her hair.  The arachnid reaches the bend in the collar and will not turn to go down and over it— so stay it stays trapped under the collar.  (They must be removed from there)

While working as an archaeologist on Shelter Island off of Eastern Long Island  my team an I often had to penetrate dense vegetative  tangles and thickets heavily infested with ticks.   Our field work required us to locate sites by subsurface probes and then excavate these areas.  The process required clearing  vegetation and then driving wood stakes to mark off excavation boundaries.  On more than one occasion our work extended over several days.  Often returning to a site after leaving the site area overnight we would find the tops of our stakes densely occupied by hungry ticks.  The stakes —which had been driven into the soil by sweaty human hands—leaving behind attractant odors for ticks to home in on from the surrounding vegetation.  Ten or more might be clustered on the top of the stake standing nearly upright with their fore appendages ready to grasp or entangle a host they expected to pass by again. .

University students in those days were well equipped with Zippo lighters and bug spray and ready and eager to deal with these aggressive and blood thirsty invaders.

But they too often resisted directions to tuck long pants into boot tops and wear long-sleeved buttoned up collared shirts—preferring more fashionable dress—like muscle shirts —to their eventual chagrin.