How to Identify Eastern Brood XIX Magicicadas.

How to Identify Eastern Brood XIX Magicicadas.

Brood XIX periodical cicadas is the largest of all the periodical cicada broods. Occurring every 13 years, it occupies the largest geographic area of the United States. These cicadas (in the genus known as Magicicada) consists of four distinct species each with their own unique male calling song and morphology.

Of the four species, only three are known to occur in the eastern United States. Massachusetts Cicadas conducted distribution survey work in Virginia in order to determine in greater detail Brood XIX's north-eastern range. Click here to view the Brood XIX distribution map.

The three species in Virginia are M. tredecim, M. tredecassini and M. tredecula. These three species are the most common and are widely distributed among Brood XIX's range. However M. tredecim is replaced by the recently discovered fourth species M. neotredecim in the north western states where Brood XIX occurs.

While similar in appearance, the calling songs of M. tredecim and M. neotredecim are distinctly different in calling frequency sound pitch. That is, M. neotredecim is higher in frequency than M. tredecim. In fact, it has been documented that M. neotredecim is the direct ancestor of it's 17 year counterpart, M. septendecim. It was found that the calling song frequency between these two species is very similar.

However where M. neotredecim and M. tredecim overlap in distribution range, then M. neotredecim's calling frequency is much higher than its M. septendecim ancestor.

I know it sounds confusing and this is perhaps a separate discussion for a future article but right now, we'll only focus on the three most common species found in Virginia and elsewhere in Brood XIX's range.

Identifying Magicicada tredecim

Of the three eastern species, Magicicada tredecim is the largest at around 1 1/2 inches long including the wings. It is perhaps the easiest to identify by its distinct orange and yellow bands on the ventral surface of the abdomen and the orange-red patches immediately behind the large compound eyes and in front of the front fore wing. Below are a series of thumbnails which show the orange-red patch. These same patches are also found in the 17 year variety M. septendecim and are also found in M. neotredecim.

Below is an extensive series of photos showing the orange and yellow ventral bands in M. tredecim males. These bands can vary in both degree and pattern in individuals but if they are present and encompass the majority of the underside of the abdomen, then it is very likely M. tredecim.

Another key indentifier for M. tredecim and shown in the below photos are orange patches in varying degrees located laterally on the abdomens as well. These lateral orange patches are found only in M. tredecim and are absent in M. neotredecim and the 17 year variety M. septendecim.

Morphological Observations in M. tredecim

After studying and photographing many specimens of M. tredecim, some morphological "curiosities" have been observed. While these observations are solely based on just that; "Observations" there is no scientific data or documentation that I have read that would support these observations at this time.

Female M. tredecim - seem to be darker ventrally on the surface of the abdomen and the lateral orange patches seem to be surprisingly absent.

Male M. tredecim - some M. tredecim males in Virginia seem to contain more black coloring where the orange portion of the ventral bands should be on the abdomen. They do still exhibit the orange patches laterally on the abdomen which would still make them M. tredecim. Again, these are just observations and are not based on any known documentation or studies. See the images below.

Identifying Magicicada tredecula

I was surprised to find this species in Virginia. Of the three species of 13 year Magicicadas, M. tredecula seems to be the least common. It was observed calling in very small groups of individuals and no large aggregations of M. tredecula were observed in Virginia.

It is a small species at around 1 inch to 1 1/4" in length including the wings. While similar in appearance to M. tredcassini, it does have a vastly different calling song and is further separated from M. tredecassini by having well-defined orange ventral bands that are located on the posterior portions of the sternites on the underside of the abdomen. It should also be noted that they are very similar in appearance and calling song frequency pitch as their 17 year counterpart in the northern broods known as M. septendecula. The only difference between M. tredecula and M. septendecula are lifecyle length.

Determining M. tredecassini

M. tredecassini is a small species. Similar in size to M. tredecula at around 1 inch to 1 1/4" in length including the wings. I like to call these guys the "angry cicada" because when they set up calling aggregations, they are very loud sometimes exceeding 90 decibels. They are generally all black in appearance including the females. Unlike the other 13 year Magicicadas they lack coloration on the abdominal sternites which makes them easy to identify when in this form. As with M. tredecula above, there are no known differences between M. tredecassini and its 17 year counterpart, M. cassini other than life cyle length.

Morphological variation in M. tredecassini

M. tredecassini and its 17 year counterpart M. cassini can sometimes exhibit ventral orange banding on the underside of the abdomen. While not as defined as in M. tredecula, this variation in morphology can sometimes confuse M. tredecassini for M. tredecula. That is why it is especially important to note which species is calling in the immediate area or capturing the specimen while it is calling if this morphological variation is noted. Below are examples of M. tredecassini exhibiting the orange banding on the abdomen but again, it is not as well defined as in M. tredecula.

Conclusions

The above outlined morphological characteristics should be able to get you started in identifying the eastern Brood XIX periodical cicada species. And if you read the article carefully you could use these same morpholigical keys to identify their 17 year counterparts for next year. Brood I is scheduled to make an appearance in West Viriginia and Virginia in 2012.

Future articles on Magicicadas will include subjects like a comparison of the three 'decim complexes in Magicicadas and identifying similarities and differences between the three. Other articles will include examining the calling song frequency pitches of the four Brood XIX periodical cicada species and how you can determine which species you are hearing by their unique calling song.