Behaviors: Cicada Emergence, Mortality and Defense Mechanisms
"Time to go top-side!! The 5th Instar Emergence"
Tibicen
Cicadas take two or more years to go from a 1st Instar nymph to the 5th
and final Instar stage. All this happens below-ground!! In total darkness,
can you believe it? Cicadas emerge from the ground in their final stage
of development known as the 5th
Instar Stage. After fighting it's way through the soil, the Cicada's
primary concern is to find a safe place to carry out it's final molt process
into adulthood. This is usually done by climbing the nearest tree which
ends up being the host plant that nourished it below ground during it's
long development.
"If I Can't Anchor, I Won't Molt Hypothesis"
Any
convenient place to molt will do just as long as it is a place where the
Cicada can firmly anchor it's legs. The thumbnail to the right demonstrates
this as the Tibicen canicularis pictured felt quite comfortable
in anchoring itself to the bottom side of my little finger. It took it a
while to find a spot that it liked but after it settled down the molt process
started. See the August
6th, 2004 journal for more pictures of this Cicada
molting on the side of my finger. Once the 5th Instar Nymph chose a
comfortable spot, I could feel it gently flexing it's legs in order to get
a firm grip.
To prove the "If I Can't Anchor, I Won't Molt" hypothesis, tests were performed in which newly emerged nymphs were held in a container made of either smooth glass or plastic and the urge to molt was impeded greatly for as long as two hours or more after emergence. The Cicada nymphs were in little compartments which kept them isolated from each other.
"4 Cicada Nymphs + 1 Jar = Very Bad Idea!!"
In the beginning of my specimen collecting, I put four (4) nymphs into a single mason jar. This proved to be less than ideal as all the cicada nymphs attempted to attach themselves to each other and attempted to molt. One cicada did not survive during the ordeal. Imagine one giant ball of nymphs wrestling with each other for the best position ON each other to molt. Not a pretty site, let me tell you.
"A Solution Found That Works for Everybody."
Fortunately,
I came up with a solution that seems to work for everyone involved. (Myself
included :P) The picture to the left shows what I came up with in order
to avoid the problem of Cicadas molting too early and to avoid them from
coming into contact with each other. This solution works quite well and
kills two birds with one stone...so they say.
"With Every Rule, there are Exceptions...Unfortunately."
There's always one bad apple that sometimes spoils it for the whole bunch. It should be noted that in one instance one Cicada started molting despite being held in a smooth plastic container. The Cicada started to molt while it was on it's back within the container with it's legs clinging to each other. I am of the mindset that this particular Cicada that started molting (due to it's limited brain power) thought it was safely anchored to something when it started molting.
Further studies for the 2005 season is needed before I can safely say that this hypothesis is a valid one.
You
can read about that instance in my Journals
for August 2004, just scroll down to August
23rd and read the story there.
"Tibicen Nymph Mortality - The Hazards of Life Above-ground."
Despite
the trials and tribulations that a nymph may face during it's juvenile developement
below ground, there are still some minor predatory issues that a nymph faces
during it's molt process. The thumbnail to the right demonstrates this.
As you can see, the Tibicen canicularis pictured was set upon by
a colony of black ants. This was due to the Cicada being stressed during
it's molt process and was unsuccessful in it's completion. The ants, in
nature's glorious design, took the stressed Cicada as an opportunity for
an easy meal.
Though I have not seen instances of this, it has been reported that Cicada nymphs can fall prey to various other ground-predators like spiders and snakes. Here's hoping I can witness this next year.
In addition, on one visit to my favorite hunting area, I noticed a T. canicularis nymph on a pine tree that was missing it's head. There was a wasp attached to it biting pieces of it's head off and flying off with them. I noticed this for an hour. It is unclear if the wasp attacked the Cicada mid-molt or noticed the Cicada was stuck and also took advantage like the ants. Unfortunately, at the time I observed this, I forgot all about my camera in order to take pictures.
It
should also be noted that I have seen instances of decimated nymphs (approximately
20 - 30) under an ash tree. These nymphs look like they were regurgitated
as if they didn't agree with the predator that ate them. It was a horrendous
site click the thumbnail to the left to witness the carnage. This is discussed
in greater detail in my Cicada
Hunt Journals for Jul 2004. Simply scroll to July
26th for the full details.
"Don't Mess with me - Nymph Defense Mechanisms"
Realistically one can say that a Cicada nymph has no defense mechanisms to speak of. However, I have noted some unusual behaviors in Cicada nymphs that can be characterized as weak defenses at best. Some of these defenses even carry over into adulthood. Read below:
Wing
Bud Flick - When handling a Cicada nymph, many times I have
noticed that a nymph will "flick" it's wing buds when
handled. This is really noticable particularly when you grasp the Cicada
nymph with your thumb and forefinger over each wing bud. This behavior is
also carried over into full adulthood when handling an adult Cicada in the
same manner.
Playing
Dead - A behavior noted in many insect species. If you're
dead, you're really not much interest to a predator. When handled a Cicada
nymph may play dead by tucking it's legs ventrally against it's abdomen
and may stay in this position for several minutes. This behavior can be
seen occassionally into adulthood.
A Long Molt Process - While probably not a true defense mechanism, the molt process for a Cicada is a slow and lengthy one. This process averages 1.5 hours or more. During this time, there is virtually no movement from the Cicada and if you are not looking for them, chances are the Cicada will go un-noticed for it's entire molt process. While Cicadas molt, they look like a normal piece of flora on whatever they are attached to and are easily missed by birds and other predators. During my observations of Cicadas I have yet to notice, with the exception of ants (and these were due to the Cicada being stuck in it's shell mid-molt), any predators spotting a Cicada during this process.
