Seventeen years ago, I didn’t care about id’ing a periodical cicada to species, but thanks to iNat, now I do. With the big emergence about to happen in my area, it’s time to get educated about the differences between:
I’d appreciate any tips from experienced observers/entomologists here who could help newbies like me start to sort them out. I bet it will aid not just my taking pictures in the field for my own observations, but in helping id the observations that will be coming in here from other folks. For instance, what set of photo angles can give you the easiest way to tell them apart? Are there other obvious distinguishing fieldmarks apart from their undersides? Thanks for advice!
Cicadamania.com gives the best info. As for photo angles, I would make sure to get one of the underside of the abdomen and the area between the eye and wing.
Thanks! So for the patch between eye/wing, it looks like septendecim has orange, the other two are dark at that spot. From the upperside, can cassini vs septendecula be distinguished in some other way?
For the underside, it looks like septendecim is fairly orangey, cassini fairly dark, septendecula sort of in between those two? Might cassini vs septendecula, or septendecim vs septendecula be harder to tell apart from just the underside depending on the individual’s shading?
I don’t think you can ID them to species with just the upperside. You could separate them into septendecim and cassini/septendecula. With the abdomen, septendecim has almost completely orange stripes, septendecula has black stripes with some orange, and cassini has a pretty much completely black abdomen.
Thanks! With that in mind I’m thinking about all the incoming observations we might see with just the upperside- where it’s too tough to call they could just be id’d to Magicicada with a note about the species similarity.
I’m a little late to this conversation, but roshan2010 nailed it when they said that the most important features are on the underside. I’m encouraging people to try to get underside shots for my project (https://www.inaturalist.org/projects/brood-x-cicadas-2021) so that we can get as many species-level IDs as possible. Genus-level IDs are valuable for mapping, but with iNaturalist, we may actually be able to get a better sense of the distribution of species within Brood X. Ventral shots also reveal whether the specimen is male/female, whether a female has mated/oviposited, and whether there’s Massospora infection.
The width of the orange stripes on the abdomen of -decula vs. -decim is the big difference; -decula’s stripes are very narrow, about 1/4 of the width of the segment, while -decim’s are wide, ranging from over 1/3 to nearly the entire segment in very orange individuals. When there’s doubt about the width of the stripes, look at the edge of the pronotum and the pleura (the area underneath the pronotum surrounding the front legs). It’s orange in -decim, but black in -decula.
I’m so excited that more people are getting into Magicicada this year! They really aren’t hard to ID, once you get the knack, but it’s important to keep location and date in mind so as not to mix up 13- and 17-year species.
I would think that since M. septendecim is probably going to be the most common species, a lot of the upperside shots would still be IDable to species as long as they show the area between the wing and eye.
It is true that the presence of an orange patch is enough to confirm septendecim ID, but unfortunately a lot of folks take completely dorsal photos, and all you can tell from those is that it’s Magicicada. Lateral photos are better, but the ventral shot is the best for ID. Once in a while, especially at the beginning of an emergence, the cicadas can be high up in trees and flighty, but most of the time, there’s no reason not to just grab the bug and snap a pic of the underside. (Maybe after you take that really pretty in situ shot.)
In my two previous experiences with Brood X in and around Cincinnati, cassini was by far the most common species; it seems to do best in open areas and suburban habitats, while septendecim favors deeper woods and high canopies. In Brood IX, there were areas where (surprisingly, to me) -decula was most common.
Me and a couple other users are looking into more consistent ways to identify these species, and we have a strong hunch about the number of ridges on the cibarium, or the roundish thing that protrudes from the face of the cicada. If you can, please take a photo of the cibarium from a direct angle, and use flash so that each ridge is visible. Thanks!
Great, it should be easy to get this kind of “snout shot”- and I notice you have a teneral as example so are they even identifiable at that stage? What degree of difference are y’all thinking about?
The number of ridges shouldn’t change during sclerotization, so identifying teneral might be possible at some stage. For that we’d need to find teneral, record their ridges, and then keep them until sclerotization, which isn’t ultimately that difficult.
The difference is only by 1 ridge per species, but I’m going to refrain from saying any specific number because it could be up to change depending on further research.
Well I have a bunch of cicadas lying around outside and a 10x lens in my pocket…
Update: Collected 20ish or so each of fully adult septendecim and cassini. I counted not the ridges, but the valleys between them, since they are typically lined with light colored hairs, counting the stripe areas until they reach a rounded, more generally hairy area at the bottom of the snout.
Septendecim tended 8 stripes but maybe sometimes 7. Cassini tended 7 stripes but maybe sometimes 8. I don’t know if the range was due to variability within species, or just my learning curve on the method.
Per comments in https://www.inaturalist.org/observations/80182004 I was thinking about how to collect data by organizing my audio/photos per individual by sequencing them in some order I can remember so I don’t accidentally lose track of which cicada pictured is making what sound when.
While I was bathing in chorus sound on the back porch, a cassini perched next to me at full blast- and then segued into an alarm call as he touched a spiderweb the wrong way as he was flying off again. Inspired by his example, I plan to fit in this field op during this week as work and weather permit:
Record male cicada with phone app while perched and singing
With recorder still running, catch cicada in hand, generating alarm call
With cicada safely held, switch to camera app, take 1 or 2 head shots, 1 or 2 abdomen shots, in some sensible order
Switch to audio app, get one more alarm call in hand, maybe at a fixed recording length to help data stay organized in the field
Release cicada, find the next one
Cons:
-Doesn’t have a good way to get measurement to the 0.1 cm without juggling an extra item- but could be aided by @graytreefrog 's hand-dotting trick
-Doesn’t allow for writing extra info down without juggling extra items- recording data by voice is impractical at field volume levels
-Singing cicadas must be in easy reach- hard at lower densities where they all congregate up high in the trees- but I am in a high density area
Pros:
-Data for a single observed individual is timestamped by the first audio recording of his singing- it’s the “index record” for his audio/photo dataset
-Recording typical song in progress can make species id unambiguous
-A direct segue from song to alarm (may take some catching practice there) can help with compare/contrast type analyses later
Comments welcome! I feel like I forgot something.
Update 6/15: Well, my data collection was only partial- all calling septendecula were out of reach whenever I went out. And now, we are on the definite downward side of the emergence here so there is a lower chance to grab some. Oh well, I’ll get some next time. ;)
