Wednesday, February 10, 2021

Periodical Cicadas


     They're coming! And in a BIG way! Billions of periodical cicadas will be emerging from mid April to the beginning of June after spending 17 years underground! These are different from the many species of annual cicadas (sometimes also called dog-day or harvestflies) which grace us with their songs each summer. Though each individual annual cicada lives 2-5 years underground before emerging, they're life cycles are staggered so we get some each year. Most annuals emerge after the last of the periodicals have finished reproducing. 
     Periodical cicadas emerge on prime numbered years, either 13 or 17. The 13 year ones are restricted to the South. There are a couple of theories why this is. One has to do with the ice ages during the Pleistocene Epoch 1.8 million years ago. Summers then were believed to be cyclical, with warmer summers each 13 or 17 years. While underground the temperatures were regulated, the adults emerged on these warmer years. This was a good adaptation as no predators could evolve to take advantage of them emerging so far apart. By all of them emerging in synchronization over a short time period, when ground temperatures reach 64 degrees Fahrenheit in a sustained pattern, usually after a rain, they overwhelm the predators that remain. Through what is called predator satiation, where animals who would eat them are flooded with so many cicadas that they can consume only a small amount, reducing the probability of an individual being eaten, many survive to lay eggs. 
     The cicadas that emerge together in the same year are collectively called a "Brood" which are labeled with Roman numerals. There were at one time 17 broods of 17-year cicadas in North America (30 overall, with thirteen 13-year ones), but now some are now extinct, and only15 survive. Take for example Brood XI which was last seen in Connecticut in 1954. The ones emerging in the DMV and other parts are parts of Brood X, the Great Eastern Brood. This is one of the larger and most widespread of them. For the first time since 2004, periodical cicadas will emerge in parts of Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York (though almost extinct (extirpated) here), Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Washington, DC. 
     While there are 3,000 species of cicadas (Latin for "tree cricket"), periodical cicadas are a rarity, with only eastern North America having them. This is a natural phenomenon where cicadas form huge choruses by species. For while they may seem the same, there are actually three species that emerge together to then attract their specific females. Each male chorus (for only the males call) has its own species specific songs to attract their mates and they group together for best effect. They last for 5-6 weeks as adults. You will start to notice the burrows as they emerge, or occasionally chimneys or mud turrets in wetter areas, that they form when digging out and then the empty molts of old skins from the emerging nymphs. The nymphs usually have shed 5 times before the final molt to an adult cicada. Nymphs ready to emerge have black spots behind their eyes, but you'll see many nymphs prior to their emergence under logs or flagstones. They will start to burrow sideways when they can't go up anymore and you'll see these the most should you lift the logs and flagstones. Most periodical cicadas have red eyes, but some also have white or grey eyes. 

Periodical burrows and a molt

    Brood X includes these three species, which are not always easy to tell apart. The Pharaoh cicadas, Magicicada septendecim, are the largest and the ones that can be found the furthest north of all the periodical cicadas. They are characterized by their broad orange stripes on their abdomen, the patch of orange between their eyes and wing, and of course their species specific song that they all have. The Dwarf cicada, Magicicada cassini, or Cassini's periodical cicada, is smaller, has no orange between the eye and wing, and usually an all black abdomen. The Decula cicada, Magicicada septendecula, is similar in size to the dwarf Cassini, also lacks an orange patch between the eye and wing, and has some orange on its abdomen. The last two are easily confused. They of course have species specific calls and only males call. While the 13 year periodical cicadas are often treated as different species, many now think they're variations of these three species that come out in their own broods of 13 years. 

A periodical cicada sheds its skin for the last time.

     Periodical cicadas, no matter which species, are often called locusts. Actual locust are grasshoppers, so why did they call cicadas locust? This goes back to the first time that a brood was seen by European settlers. In 1633, in the Plymouth colony in Massachusetts, a large emergence of periodical cicadas was reported. This was shortly followed by what they called a "pestilent fever" that raged through the colony and the Indian neighbors. This was close enough to the biblical plagues that included locusts in huge numbers to ensure that name for them. It was a new experience for the colonists and the only thing they could compare it was the locust plagues of the bible. 
     And though the biblical proportions of the cicadas is still hard to believe, and though they pale in comparison to what they used to be, the billions that will arrive will be of epic proportions. Cicadas are known to be among the loudest of insects. Choruses of males singing can reach from 100-120 decibels. This is enough to affect many people with sensitive hearing. This as loud as a rock concert, but will last for many, many days. Interestingly enough, the sound of leaf blowers, power tools, and lawn mowers may attract them. Such chores are best left to early morning or late after noon to avoid any such confusion. 
      The females twitch their wings in response to the males songs when they accept a male to mate with. Once they've mated, the females search for places to lay their eggs. While adult cicadas don't really feed very much, except for some harmless sucking of some plant sap, the egg laying is what people worry about. For the 3-4 week adult life span, mated female cicadas use their ovipositors to slice into pencil-sized twigs to lay their eggs. They lay 24-48 eggs into the slits they carve out until they reach the 600 more so eggs they're allotted. 

Flagging damage by cicadas inserting eggs into stems.

     The egg laying inside these slender twigs causes many to die off. They often wilt and hang down, while others may break off. The wilted and hanging branches are referred to as flagging. Cicadas are picky as to which tree (they don't disturb plants or ferns) they choose to insert their eggs in. They are usually 6 feet or more tall, mostly at the edge of mature woods, where's there some sun, and usually have pencil-sized stems to oviposit in. They tend to avoid lawn areas with small shrubs unless they're near mature woods. For those people who were around the last time cicadas emerged, they normally use the same places to try and lay eggs again. They don't like to use any evergreens, sumacs, pawpaws, many viburnums, euonymus, or Osage orange. Studies have shown that healthy trees don't show long term ill affects, even in orchards which have do not show any decrease in fruit yield. Think of it as natural pruning that has been going on for millennia. If you do want to be cautious, leave your tree planting until the fall. Or protect your trees with 1.0cm netting (but beware that this may trap birds and snakes), but make sure they don't get branches poking through, place only after egg laying has started (which is at the end of May early June around here), and remove then when the egg laying is done. Leaving it on too long will affect the tree itself through distortion of growth patterns and can lead to increase in diseases. It can also affect pollination efforts by other insects. One thing that did Not help was the use of pesticides. Studies have shown that this did not make a difference in egg laying. The young nymphs hatch out after 6-10 weeks and burrow underground to feed on tree roots for 17 years.

Evidence of egg slits left by cicada ovipositor.

     Now many animals feast on the cicadas, including things you don't normally think of eating them such as squirrels, chipmunks, turkeys, and even copperheads. Many animals, especially birds, will benefit and rear more young due to the extra food supply. Dogs and cats will also feed on them, and this where you may want to be cautious. Cicadas are edible (more on that in a second), but eating too many of the hard shells may cause digestive issues in pets. They do make good bait as some people have learned. I caught a huge carp on one that had decided to surface feed.

A house sparrow feeds on a periodical cicada

     So I did mention they were edible, which includes by people? The native American tribes would consume them when they were available. They've been called the "shrimp of the land" and that is true. They are both arthropods and can make good meals. People every year start to practice entomophagy (eating of insects) when they appear. Don't be surprised to see some of the local restaurants including them on their menus. It's not just countless wildlife species who relish them.

A freshly emerged, or teneral, cicada, still white and soft.

     Cicadas are gluten free, low in fat, low carb, rich in protein (the same pound for pound as beef). They've been grilled, skewered, steamed, barbecued, blanched, boiled, blanched, and used in cocktails. My old boss would fill the empty skins with Cheez Whiz and serve them as appetizers. But there are a few things you want to know if trying them (I know I will again!). First of all, they are best when their teneral, meaning freshly molted adults. Get them while their white and soft, before the chitin on their shells have hardened, you don't need all that crunch. Collect them from places that have not been exposed to pesticides and herbicides. As they come up from the ground at night and in the early morning to climb anything they can molt on, that's the best time to get them. Pull off the legs and wings as well. With a bit of Old Bay, they really do taste like seafood. You can see me eat one here: (15) Capital Naturalist: Eating Cicadas - YouTube

The author tastes one yet again...

     Or you can eat them raw, which is likely the least desirable way to eat them:           
But care should be taken when trying them. First of to be aware of shellfish allergies. Secondly, some studies have shown they do accumulate mercury (again if you're just trying one, not  big deal). But also, be aware that this is a limited resource and we do want to let them reproduce and continue this natural phenomenon. 
     Periodical cicadas emerge and mate well before cicada killers emerge to paralyze the annual green ones to feed their young. More on cicada killers in this blog I put together: Capital Naturalist by Alonso Abugattas: Cicada Killers or Cicada Hawks.  One thing that periodical cicadas can't elude is the Massospora fungi that infects them. This fungus fills their abdomens and destroys their ability to reproduce. Sometimes the entire abdomen falls off. 
     So some of you may remember seeing some earlier than the 17 years. This pre-emergence happens quite a bit. These stragglers, as they're called, usually come especially come out 4 years earlier. This has led to the theory that these actually may be the 13 year ones that some classify as different species. For more on this, check out this blog I did on them: Capital Naturalist by Alonso Abugattas: Periodical Cicadas Early Emergence
     So enjoy this natural phenomenon while you can. These "locust" don't spread disease or eat our crops. They can provide benefits such as aerating the soil or providing food for countless creatures. The next time we can hear and see this unique event won't be until 2038.