dan_johnson's Journal

Procambarus simulans and P. curdi are two closely related species that are
easily identified as adults and subadults, but for which very few iNaturalist
observations provide adequate photos to make such identification possible.
In west and southern Texas, range can be used to identify the species; however, in
NE Texas and SE Oklahoma, both occur together making range not useful for identification.
This guide will show what features need to be photographed to allow observations of
these two species to be identified.

The two species, insofar as is currently known, are only identifiable by
features of the gonopod (male) or the annulus ventralis (female).

Below is a picture of the ventral surface of a Procambarus simulans male
with the pair of gonopods indicated by the dashed red circle. The photographs should
be taken at this angle with focus on the apex of it's left gonopod
(one on right in photo).




Below is a closeup of the apex of the gonopod of Procambarus simulans.
What is pointed to is the caudal process; in P. simulans it is flattened so
it's widest in this view:

In contrast, the image below is from the same angle for Procambarus curdi. Here
the caudal process is flattened in a nearly perpendicular direction, so it appears narrow
in this view.

In the two images above, notice the right gonopod (one on left in photos). This same
process is in the perpendicular direction, so appears very narrow for P. simulans and very wide for P. curdi.

The above views should be sufficient. Another gonopod view that is alternatively be
useful is the "end on" view. Below is that view for P. simulans.

In constrast, the next image is for P. curdi. Notice the strikingly different
orientation of the caudal processes for the two species.

Males of these two species can be distinguished with such photos most easily
in adults, but also to a lesser degree in subadults.

Warning!!! Simply taking a photo of the region of the gonopods is almost never adequate. The
apices must be clearly visible. In many, many existing observations, the gonopods are
covered with hair, various debris, and often obscured by the 2nd pair of swimmerets
(gonopods are the first pair).

Females can be distinguished by different sinus shapes of the annulus ventralis
(sperm receptacle). Below
is a female P. curdi indicating the annulus ventralis.

The two images below show a P. simulans annulus ventral without and with the sinus
highlighted:

In contrast, the pair of images below illustrate the sinus of P. curdi

Females of these two species can usually be distinguished by such photos for adult to
fairly small juvenile sizes.

Warning!!! Simply taking a photo of the ventral surface of the female, as is often done,
is rarely adequate for identification. The sinus of the annulus ventralis needs to
be clearly visible. In many existing photos it is obscured by hair and debris.

I started annotating large numbers of teneral cicadas as such. To do this for a given observation, I go to an observation and then under "Observation fields," I type "teneral." It gives you the option of selecting "Yes," "No," or "Maybe." I alway select yes, since I'm doing this only for tenerals. I then push "Add" and it's done. After the first time, "teneral" shows up in the "Observation fields" menu, so you won't have to type it.

So far the number of cicadas annotated as teneral number 1254. I have focused on the southeastern and central U.S. so far. You can see them here: https://www.inaturalist.org/observations?place_id=97394&taxon_id=50190&field:teneral=yes . Note the "&field:teneral=yes" part of the URL. This can be added to any explore or identify URL to restrict the observations to tenerals.

What is the value of such annotations? It will help us better understand how to identify them as they are more difficult to identify than fully hardened specimens. One can browse given species, to develop a feel for the appearance of their tenerals. For example, here are all the teneral Neotibicen superbus, via identify:

https://www.inaturalist.org/observations/identify?reviewed=any&quality_grade=needs_id%2Cresearch&taxon_id=469277&field%3Ateneral=yes

To look at the tenerals for a given species, simply go to identify and select the species of interest, under Filters, toggle on "Research grade" and "needs Id" and select Reviewed as "any" and push "Update search." The add "&field:teneral=yes" to the URL and hit the return key. You can then browse as many as you like.

Unfortunately the current state of affairs is that a lot of tenerals are misidentified, so keep that in mind as you browse. I like to pay particular attention to those identified by @billreynolds, @rlsanders, @easmeds and @willc-t four experts on US cicadas. Those identified only by others are very likely to be misidentified.

I encourage @willc-t and @easmeds and others to annotate any tenerals they see.

I did some inaturalist observing in Idaho, my home state, for a few days recently, while visiting family. Idaho has a total of only 54,802 observations for the whole state, compared to 2,059,416 for Texas. That's 37 times as many observations for Texas. When looking at the populations; however, Idaho is home to 1.7 million people compared to 28.7 in Texas, with the Texas population being 16.8 times the Idaho population. Taking this into account, Idaho has half the observations per capita as does Texas.

A monograph I authored has just been published in Zootaxa. It's titled "The subgenus Ortmannicus (Decapoda: Cambaridae) in Texas, with descriptions of new species." Included are three new species:

Procambarus albaughi
Procambarus fayettei
Procambarus parvus

If anyone wants a reprint, let me know.

Over the last 10 years on iNaturalist, the number of crayfish observations each year has been between 1.5 to 2.1 times the number observed the previous year. During the last five years, the number has been very close to 2 (1.8-2.1). Here is the breakdown of number of observations and factors for each year:

2743 2.0
1402 1.8
761 2.1
367 1.9
195 1.8
106 1.7
63 1.5
41 1.6
26 1.5
17 --

There was 161 times the number of crayfish observations during the last year than there was during a year ten years ago. I think this trend follows the same trend for iNaturalist as a whole. How long will this amazing trend continue?

How to photograph crayfish for inaturalist

In order for crayfish to be adequately identified, it is helpful to provide
a variety of views of the crayfish. Dorsal and lateral views should be
always provided:

In the dorsal view, make sure both the areola and rostrum are
visible:

Lateral view:

Of utmost importance for many species are photos of the gonopod (for
males) or annulus ventralis (for females).

The following image shows the ventral view of an adult male crayfish.
The gonopods are its reproductive organs. They are normally tucked
between the walking legs.

It will often be necessary to pry one into
view with a toothpick or probe. The most useful views are from a
lateral or mesial aspect.

Try to get a closeup view clearly showing the features at the tip:

The following is an image of the ventral side of a female. A closeup
photo of annulus ventralis is very helpful (small round feature between
the last two pairs of walking legs).

Try to get a clear closeup of the annulus ventralis and surrounding area
as follows.

Additional views that may be helpful for identification include:

The chela (claw)

Any hooks present in adult males

The tail fan

40 years ago when I was in my mid teens living in Arlington, Texas, I would climb trees to collect the various cicada species calling in the area. Back then there was seemingly no way possible to even remotely identify anything, but it was nevertheless interesting to see the different varieties. Fast forward to today, a young person would easily get all of the species identified by posting them on inaturalist.

I find my interest in cicadas rekindled to some extent and am enjoying learning all the different species that occur in Texas.

The crayfishes Procambarus clarkii and Fallicambarus fodiens are approximately equally abundant in Texas, yet currently there are fifty times more clarkii observations (257 vs. 5).

https://www.inaturalist.org/observations?place_id=18&quality_grade=any&taxon_id=51221

https://www.inaturalist.org/observations?place_id=18&quality_grade=any&taxon_id=100848

The difference is that clarkii inhabits areas such as ponds, lakes and streams where they are likely to be seen by humans, whereas fodiens occurs more in ditches and field, and spends most of their time hidden in burrows.