Monday, September 15, 2008

My Theory About Crickets

Yesterday I did a whole bunch of things. In the morning I did a hike with Professor Chuck up in Jeremy Ranch to check out a new hybrid oak I found a couple weeks back (it’s a biggie- a star of my upcoming hybrid oak series.) In the afternoon I took the Trifecta out birthday-shopping for the Awesome Wife, whose “39th” is coming up later this week. And then in the late afternoon/early evening I did an easy mtn bike ride up around Pinebrook.

What did these 3 activities have in common? Just this: the whole day, wherever I went, I heard crickets chirping. And so this is as good a time as any to go off on my Late Summer Day-Chirping Theory of Crickets.

Tangent: Like pretty much all of my "theories”, this is of course more of a “hypothesis”, since it’s not based on any real hard science or data or experimental results, so much as it is just me going off half-cocked… But I like saying that I have a “theory”, because then the idea sounds somewhat “weightier”…

The “theory” is based on my observation over the last several years that in the early and middle summer. Crickets chirp at night, but rarely during the day. But as you get into late August and through September, it seems like crickets chirp pretty much all day long. Why is this?

Necessary Geeky Cricket Background

Crickets” include all insects in the family Gryllidae, which is defined as the family of “true crickets”, and does not include various cricket-like insects such as Katydids, Grasshoppers or Mormon “Crickets.” Even so, there are over 900 species of Gryllidae worldwide. But the nice-sounding bugs we hear at night are specifically Field Crickets, which belong to the sub-family Gryllinae (yes, it’s the same exact word except with the “d” replaced with an “n”- way confusing...)

There are 20 species of Field Cricket, representing 7 different genera in the US and Canada. 3 of those species, representing 3 of the 7 genera, are exotics, brought from the old world- deliberately or accidentally- by humans. Of the remaining native species, the most widespread (and to my knowledge only field cricket here in Utah) is Gryllus pennsylanicus. G. Pennsylvanicus is found pretty much all over the lower 48 states with the big exception of the Southeast and Gulf Coast, which have their own impressive array of crickets.

All true crickets chirp by rubbing their fore-wings together. Only male crickets (pic below right) chirp. There are supposedly at least 4 different chirps: a “trolling” chirp (my term), calling out to any nearby females, a “courting” chirp, targeting a specific nearby female, a Warning chirp, indicating the presence of a nearby predator, and what appears to be a “post-coital” chirp, the function of which I don’t know, but seems analogous to a post-coital cigarette in the human world.

Bugs don’t have mammal-style ears, but many bugs can “hear” via different organs. In the case of crickets, they have an ear-like organ, complete with a little tympanic drum, on the insides of their knees. Females deposit fertilized eggs- up to 400 per season underground. All adult field crickets die come winter, but their eggs survive, hatching in the Spring and repeating the cycle anew.

The obvious reason why field crickets chirp at night most of the season is because there are a lots of things that eat crickets- birds, squirrels, shrews (not to mention a parasitic fly which lays its eggs on live crickets) and these things generally have an easier time finding crickets during the day. So crickets generally lay low during the day and wait until nightfall to start singing.

Tangent: You’ve probably noticed that day or night, if you try to locate a cricket by honing in on its chirp, when you get close enough it usually has the good sense to shut up. Evolution has clearly favored crickets that shut the hell up when something big is looming over them.

So Why Chirp By Day?

OK, so we know why they chirp, at night, and we know why they shut up during the day. But why do male crickets chirp at during the day at the very end of the summer? My theory: Because they have nothing to lose.

A male cricket who gets eaten/taken out back in June loses a huge opportunity- the chance to mate dozens of times throughout the summer and leave hundreds of offspring. But by mid-September, time is running out. The cricket has at most a few weeks to live. To hold back now during the day means, at best, mere days of additional life. And so the male crickets put it out there; they chirp day and night, trying to mate one last time before the frost gets them.

I’m not suggesting that male crickets sit around consciously noodling this out, like an MIT student gaming a casino or something. Rather I think that male crickets who tend to chirp by day as the days become shorter tend to produce slightly more offspring than crickets who stay day-silent till season-end, and thereby transmit more of their late-season-day-chirping genes to the next generation of G. pennsylvanicus.

I like my cricket theory for 2 reasons. First, it’s cool to think about why stuff happens the way it does in the world around you. Second is the weird applicability to us; in our own lives, we’re repeatedly presented with decisions that entail risks. And in our own way, we’re just like the crickets- our time is limited. We probably won’t die this winter, or the next, but one of these years we will die. The key to life is figuring out when to day-chirp.

6 comments:

The Martinduo said...

Hey Watcher,
I just found your cricket blog via Google. I'm doing a (free) iPhone app about cricket calls. It's a learning exercise for me to learn iPhone programming. I would love to extract your theory to provide as info in the app. "bruce at martinduo dot com"

Watcher said...

Bruce- go right ahead. Keep in mind though that the "theory" is just conjecture.

Anonymous said...

Love love love this blog. My dad just passed away a few weeks ago. He was a nature lover to no end, and he taught me everything there is to know about all animals and creatures. I never got a chance to ask him why crickets chirp in the daytime at the end of summer. I'm sitting in my backyard in Delaware now, wondering if anyone else ever noticed this. I love your theory, and I do agree that this theory should most definitely apply to our lives..

Watcher said...

Anon- I'm sorry about your Dad. He sounds like a great guy, and how lucky for you that he shared with you so much of his knowledge and passion for the natural world. I hope your memories of him are a source of comfort to you in the short-term, and happiness in the long.

Anonymous said...

Seasonal and Daily Chirping Cycles

http://kb.osu.edu/dspace/bitstream/handle/1811/5307/V67N04_200.pdf

Anonymous said...

Thank you Watcher, that was one of the most gracefully put compliments I have heard about my father since he passed. I have shared this blog with my family, and continue to listen to those crickets in my backyard- giving it everything they have got all day long!