Working on translating a key to the European shield bug nymphs (Puchkov, 1961) I thought I would look for pictures of the earlier life stages (nymphs, Fig. 1) of shield bugs (Pentatomoidea) on iNaturalist and found few observations actually had the life stage annotation. I do not have the exact numbers of Europe as a whole at that point in time, but Denmark currently has around 19.8% and the United Kingdom has around 29.4% of the observations annotated (GBIF.org, 2023).
Figure 1: Fourth instar nymph of Nezara viridula (Linnaeus, 1758). 2023.vi.22, Bad Bellingen, Germany.
So I set out to add those annotations myself instead, starting with the Netherlands, followed by the rest of the Benelux, Germany, and Ireland. Last Monday, I finished the annotating the observations of France. These regions total to about 80 000 observations, of which I annotated a bit more than 40 000 (again, I do not have the exact numbers from before I started).
Methods
I made these annotations on the iNaturalist Identify tool which has plenty of keyboard shortcuts that I found after using the mouse for 2000 observations. This allowed me to develop some muscle memory, and I ended up annotating a single page of 30 observations in around 60 seconds, so 2 seconds per observation. Most of that time was usually spent waiting for the images to load, and there were plenty of small glitches in the interface to further slow me down (including a memory leak requiring me to reload every 10-ish pages).
I was not able to annotate 715 of the verifiable observations (i.e. those with pictures, a location, and a time). In some cases, the pictures were simply not clear enough (or taken too closely) for me to determine with certainty the life stage. Another issue I had to work around were observations of multiple individuals at different life stages. Common were observations of egg clusters and just-hatched nymphs of Halyomorpha halys (Stål, 1855); the “parent bug” Elasmucha grisea (Linnaeus, 1758) doing parenting; kale plants infested with adults and nymphs of Eurydema; and adults of various species in the process of laying eggs. However, there were also many observations containing multiple pictures where one was of an adult and a second of a nymph, with no indication that it was the same individual at different times. There is currently no way to annotate multiple life stages on a single observation on iNaturalist except through non-standard observation fields, which are a lot more laborious to use and can be disabled by users.
Results
Coloring the observations by life stage on a map clearly shows the effect of the work, with the aforementioned countries covered in red; and the most of the rest of Europe in blue (Fig. 2). (There are two other notable red patches, in Abruzzo, Italy and in Granada, Spain. These are not my doing, and seem to be caused by two prolific observers annotating their own observations, respectively esant and aggranada.)
Figure 2: Map of research-grade iNaturalist observations of Pentatomoidea in Europe, colored by whether or not they have a life stage annotation.
These annotations mean additional data is available on the seasonality of these species. For example, looking at the four most observed species already reveals that Pentatoma rufipes (Linnaeus, 1758) overwinters as nymphs, whereas the other three species overwinter as adults (Fig. 3). The larger volume of data also means that more detailed analyses with more explanatory variables can be carried out. For example, the effect of climate change on the life cycle of invasive species like H. halys.
Figure 3: Seasonality of nymphs and adults of the four most of observed shield bug species.
In addition, for less common species the classification of life stages makes it possible to find more about the morphology of the earlier life stages of these species. This is useful for individuals who are working on keys (such as me), but perhaps also for computer vision models. Classifying the not-yet identified observations of nymphs as such also allows for more targeted searches by identifiers, potentially leading to even more research-grade observations of rarer species.
It should be said though, that even Chlorochroa pinicola (Mulsant & Rey, 1852), which is not particularly common in West Europe, still has many more validated pictures on Waarneming.nl than on iNaturalist. In fact, nearly half (43.2%) of all observations with images of Pentatomoidea in Europe are in the Netherlands. These are not all annotated with a life stage though, and the Observation.org platform (which Waarneming.nl is part of) seemingly only allows curators and observers add life stage annotations to an observation.
Luckily, iNaturalist does allow for this and enables me to contribute hopefully valuable data to GBIF for further analysis, by myself or by others. I will continue adding annotations — I have now started on the observations from Switzerland, luckily a lot fewer than those from France. At the same time, I am maintaining the high rate of annotation in the countries I have already annotated. In August, this means annotating about 200 observations per day (10–15 minutes) which is entirely doable. It does quickly start to add up if you are on holiday for a week, as you do in August, but that is still fewer observations than the entirety of France. Still, for this reason I hope other identifiers (or even better, observers) start annotating more as well.
References
- GBIF.org. (2023, August 11). Occurrence Download [Darwin Core Archive]. The Global Biodiversity Information Facility. doi:10.15468/DL.NXCTJW
- Puchkov, V. G. (1961). Shieldbugs. In Fauna of Ukraine (Vol. 21, Issue 1). Naukova Dumka.
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