Music for a Summer Evening

 

Posted by John Murgel, Douglas County Extension

The “dog days” of summer bring with them some of the most noticeable insect activity of the year—the sounds of insect calls.  Step outside during the afternoon or evening and you’re likely to hear a raucous mix of invertebrate “vocalizing”.  Here are three of the most common.

1. Crickets.  You’re probably familiar with the black, ground-dwelling Field Cricket.  And yes, they chirp.  But in areas with trees and shrubs (like most neighborhoods!) one of the most audibly noticeable crickets is the tree cricket.  They are green and slender and smaller than field crickets, and spend most of their lives in trees and shrubs.  Last year one of these managed to find its way into my house, and I can attest that they are loud.  Shockingly so.

     Primarily carnivorous (preying on other insects), the only plant damage that they cause is during egg-laying, when females make small wounds in twigs in which to oviposit.  These wounds can be unsightly as the plant grows over them, and may become entry sites for fungi.  The Showy Tree Cricket is famous for chirping in correlation with temperature.  Count the number of chirps you hear in 15 seconds and add 40—you should have the temperature in Fahrenheit!  Good luck doing this when it's hot.  

A tree cricket 

2. Cicadas.  Colorado is home to several species of cicada, though the famous “periodical cicadas” are not among them (they occur mostly east of the Mississippi).  The largest and loudest cicadas we have get going in late summer.  The “Plains Harvest-fly” (Megatbicen dealbatus) and “Giant Grasslands Cicada” (M. dorsatus) are most common.  In order to attract females, males “sing” by using tymbal organs on their abdomen, producing sounds that are amplified by resonating throughout the insect’s body (much like the resonator on a musical instrument).  Adult cicadas usually live a month or two, but their juvenile phase, which takes place underground, can last several years.

Dog-day cicada, head on!

3. Katydids.  In Colorado, the most common katydid is the Broadwinged Katydid, Microcentrum rhombifolium.  They mature in late summer, and are quite large—up to two inches from head to wing-tips.  They are well camouflaged, being green with very leaf-like venation on their wings.  Unlike their eastern relative, the “true” Katydid, Broadwinged Katydids do not make a “katy-did” call, rather they click and hiss softly by using specialized structures on their wings.  You might find katydid egg masses on twigs in your trees or shrubs; they are flat, tan, and laid in a double-row often resembling shingles or scales.  They are laid in late summer and fall and won’t hatch until the following spring—keep an eye out for them while you’re doing your wintertime pruning!

An adult broadwinged katydid. 

If you can’t get enough bugs, or just wonder what insects and other arthropods you  might see out and about in our state, check out the Arthropods of Colorado site, developed by CSU Extension’s entomology program.