NATURA SLOVENIAE 25(2): 53-60 Prejeto / Received: 20. 11. 2023 
SHORT COMMUNICATION Sprejeto / Accepted: 3. 12. 2023 
 
DOI: 10.14720/ns.25.2.53-60 
 Biotehniška fakulteta Univerze v Ljubljani in Nacionalni inštitut za biologijo, Ljubljana, 2023 
 
 
 
Observation of heterospecific mating attempt by blue 
chaser Libellula fulva Müller, 1764 and broad-bodied 
chaser L. depressa Linnaeus, 1758 (Odonata: 
Libellulidae) 
 
 
Matjaž BEDJANIČ
 
 
 
National Institute of Biology, Večna pot 121, SI-1000 Ljubljana, Slovenia; E-mail: matjaz.bedjanic@nib.si 
 
 
Abstract. A successful copula formation between a Libellula fulva male and a L. depressa female was 
documented photographically on 23. 6. 2022 along a small stream at the Natura 2000 site Ličenca pri Poljčanah in 
NE Slovenia. This represents the first record of an anomalous mating attempt with copula formation between the 
species involved. Their distribution in Slovenia as well as syntopic and syntemporal observations in the country are 
presented and briefly discussed, as are the site-specific factors and aged female colouration that may have 
contributed to the described rare attempt of heterospecific mating. 
 
Key words: Odonata, dragonflies, mating, copulation, wheel position, syntopic occurrence 
 
 
Izvleček. Opazovanje poskusa heterospecifičnega parjenja črnega ploščca Libellula fulva Müller, 
1764 in modrega ploščca L. depressa Linnaeus, 1758 (Odonata: Libellulidae) – Dne 23. 6. 2022 je bila 
ob manjšem potočku v območju Natura 2000 Ličenca pri Poljčanah v SV Sloveniji foto dokumentirana uspešna 
formacija paritvenega koleslja med samcem črnega ploščca Libellula fulva in samico modrega ploščca L. depressa. 
To je prvi zapis o poskusu parjenja s formacijo paritvenega koleslja med vpletenima vrstama. Na kratko so 
predstavljena in obravnavana njuna razširjenost v Sloveniji ter prostorsko in časovno prekrivajoča se opazovanja v 
državi, prav tako pa so obravnavani specifični dejavniki na mestu opazovanja in obarvanost postarane samice, ki 
bi lahko prispevali k opisanemu redkemu poskusu heterospecifičnega parjenja. 
 
Ključne besede: Odonata, kačji pastirji, parjenje, kopulacija, paritveni koleselj, sintopično pojavljanje 
 
 
 
Introduction 
 
 
Dragonflies (Insecta: Odonata) have a unique mode of reproduction among insects with 
indirect insemination and delayed fertilization. In order to reproduce, sexually mature 
dragonflies must encounter a conspecific of the opposite sex, recognize it and mate with it. Prior 
to copulation, sperm is transferred from the male's primary genitalia at the tip of the abdomen 
to his secondary genitalia at the base of the abdomen, and during the formation of the heart-
shaped copula or mating wheel, it is transferred to female's genitalia. The eggs are not fertilized 
until they are laid. Recognition of sex and species in most odonates is primarily based on visual 

54 Matjaž BEDJANIČ: Observation of heterospecific mating attempt by blue chaser ... / SHORT COMMUNICATION 
NATURA SLOVENIAE 25(2): 53-60 
characteristics such as size, body shape, flight style, colour and colour pattern (Corbet 1999; 
Wildermuth & Martens 2019).  
 
Reports of anomalous mating attempts between different dragonfly species are not 
extremely rare, and comprehensive reviews on this topic have been presented by e.g.  
Bick & Bick (1981), Utzeri & Belfiore (1990), and Corbet (1999). They include both observations 
of homosexual heterospecific male tandems, as well as heterosexual heterospecific pairing 
attempts. The latter usually include observations of interspecific tandems within the same genus 
(e.g. Heidemann 1982; Miller & Fincke 2004; Chovanec 2022), less frequently combinations 
between representatives of different genera (e.g. Bedjanič 2006; Wildermuth 2015), or even 
between different families within the same suborder (e.g. Corbet 1999; Kosterin et al. 2001; 
Tamm et al. 2015). In most instances, the anom alous mating attempt ends in the tandem stage, 
before the contact of male’s secondary copulation organ and female’s genitalia and thus prior 
to actual sperm transfer. Less commonly, the heterospecific mating wheel is formed, which is 
an obligatory stage in the functional framework for potential insemination and subsequent 
fertilization. The reports of subsequent oviposition after heterospecific copulation are much rarer 
(e.g. Kunz 2010), while reports on confirmed interspecific hybrids in dragonflies are only 
occasional (Corbet 1999; Futahashi & Hayashi 2004, Okude & Futahashi 2022; Solano et al. 
2018). 
 
Within the family Libellulidae, heterospecific mating errors were most frequently reported in 
Sympetrum species, either as intrageneric pairs (e.g. Bick & Bick 1981; Rehfeldt 1993; Kornová 
et al. 2022) or more rarely heterogeneric pairs (e.g. Rehfeldt 1993; Richardson & Smith 2012; 
Wildermuth 2015). In other libellulid genera, such as Leucorrhinia (e.g. Utzeri & Belfiore 1990) 
and Orthetrum (e.g. Khelifa 2013; Chovanec 2022; Thio & Ngiam 2023), reports are sparser. 
Nevertheless, with rare exceptions (e.g. Ku n z 2 0 1 0 ) , t h e g r e a t m a j o r i t y o f r e p o r t s o n l y 
documents tandem formation, without actual copulation, i.e. without the formation of a mating 
wheel. In the genus Libellula, individual cases of heterospecific copulation have been reported 
in the Nearctic (Bick & Bick 1981) and Oriental species (Utzeri & Belfiore 1990), while only a 
few scattered reports are known for European representatives of the genus – e.g.  
Seggewiße (2008) documented an apparently unsuccessful attempt of copula formation 
between a L. fulva male and a L. quadrimaculata female, while Wildermuth & Martens (2019) 
briefly mention exceptional cases of anomalous mating attempts between L. depressa and  
L. quadrimaculata. A further observation of heterospecific copulation between a L. fulva male 
and a L. depressa female, not previously reported in the literature, is added in this article. 
 
 
 
Materials and methods 
 
 
The observations described in the sequel were made on 23. 6. 2022 at the Natura 2000 site 
Ličenca pri Poljčanah in NE Slovenia. The locality is a small right tributary of the Ličenca stream 
at the bridge of the Ponevnik–Zgornje Laže side road, 200 meters N of the settlement of Zgornje 
Laže (WGS 84 Lat./Long.: 46.3223 °N, 15.5396 °E). The aforementioned small tributary of the 
Ličenca stream is less than 1 meter wide, the water current is slow and the richly overgrown 
riparian vegetation almost completely covers the water surface. On the upstream side of the 

Matjaž BEDJANIČ: Observation of heterospecific mating attempt by blue chaser ... / SHORT COMMUNICATION 55 
NATURA SLOVENIAE 25(2): 53-60 
bridge, a small widening is present, forming a shallow 1.5 × 0.5 m wide pool, overgrown with 
Sparganium sp. and some clumps of Carex sp. and Iris pseudacorus, but still with some open 
water surface. The surrounding landscape is an open mosaic agricultural land, upstream of the 
bridge on one side there is a regularly mown semi-intensive meadow, while the other side is 
bordered by a field. Along the stream there is a narrow, unmown belt of vegetation with a few 
small Salix shrubs. 
 
The observations on site were made from the road bridge. In the afternoon, between  
15:15 and 15:25 p.m. (Central European Summer Time), the weather was predominantly sunny 
with 25
o
C, very light cloud cover and no wind. Photographs were taken with the Sony Cyber-
Shot RX10 IV digital camera. The precise time of each individual photograph was subsequently 
determined at home using the automatically saved image properties. 
 
 
 
Results and discussion 
 
 
On arrival at the site, already known from previous visits, regular rapid dragonfly inventory 
was carried out from the road bridge. Soon, a somewhat strange, restlessly flying tandem was 
spotted, and only seconds later I realized that it consisted of a L. fulva male and a L. depressa 
female. Apparently, the female was trying to free herself from the grasp of male’s appendages, 
but was unsuccessful. The pair in tandem was restless, the potential mates repeatedly settled 
down for a few seconds and then flew off again and changed position. After observing this 
behaviour for about a minute and being unable to take a photo, the first observed copula was 
formed at around 15:19:40 (Fig. 1a) and lasted less than 15 seconds. Then the copula disbanded 
and the pair still remained in tandem at the same location. From above, at a distance of a few 
centimetres and without any contact, it was harassed for a few seconds by a flying L. depressa 
male (Fig. 1b). After changing position and flying around at short intervals, the pair successfully 
formed the second copula at around 15:20:25, whereupon several successful photos were taken 
(Fig. 1c, d). The pair in the copula changed position on Sparganium leaves once or twice, but 
remained in the copula at least until 15:22:12, when the last photo was taken. After that, visual 
contact with the pair was lost, and they did not return to the same location for the next two or 
three minutes before I left. Other dragonfly specimens observed during my brief visit to this 
locality were: Calopteryx splendens 2♂, 1♀, Coenagrion ornatum 2♂, 1♀, C. puella 1♂, 
Platycnemis pennipes 3♂, 1♀, Orthetrum brunneum 3♂, O. coerulescens 4♂, 1 copula and 
Libellula depressa 2♂. 
  

56 Matjaž BEDJANIČ: Observation of heterospecific mating attempt by blue chaser ... / SHORT COMMUNICATION 
NATURA SLOVENIAE 25(2): 53-60 
 
Figure 1. Temporal sequence of successful copula formation between a Blue Chaser Libellula fulva male and a Broad-
bodied Chaser L. depressa female: (a) first successful copula formation (15:19:52 p.m.), (b) copula breaking up, pair 
remains in tandem, harassed by a Blue Chaser L. depressa male from above (15:20:00 p.m.), (c) second successful 
copula formation (15:21:00 p.m.), (d) after changing the resting place the pair still remains in second successful copula 
formation (15:21:34 p.m.) (photo: M. Bedjanič, Ličenca pri Poljčanah, 23. 6. 2022). 
Slika 1. Časovno zaporedje uspešne formacije paritvenega koleslja med samcem črnega ploščca Libellula fulva in samico 
modrega ploščca L. depressa: (a) prva uspešna formacija paritvenega koleslja (15:19:52), (b) razpad paritvenega 
koleslja, par ostane v tandemu, ki ga od zgoraj nadleguje samec modrega ploščca L. depressa (15:20:00), (c) druga 
uspešna formacija paritvenega koleslja (15:21:00), (d) po spremembi počivališča par še vedno vztraja v drugi uspešni 
formaciji paritvenega koleslja (15:21:34) (foto: M. Bedjanič, Ličenca pri Poljčanah, 23. 6. 2022). 
 
 
The basic prerequisite for potential heterospecific sexual interaction is clearly the 
simultaneous occurrence of adult dragonflies in space and time. Regarding the known 
occurrence of both species in Slovenia, the database of the Slovene Dragonfly Society and the 
Centre for Cartography of Fauna and Flora (as of October 2023) contains 571 localities with 937 
faunistic data for L. fulva, while L. depressa is much more common with 2,200 known localities 
and 3,768 faunistic data (Fig. 2). More importantly, both species were recorded at the same 
locality in 337 cases with 814 faunistic data. Their co -occurrence on the same date was recorded 
at 279 localities for which 375 such faunistic data are available, the latter meaning the 
simultaneous observation of both species at the same location and on the same date. 
  

Matjaž BEDJANIČ: Observation of heterospecific mating attempt by blue chaser ... / SHORT COMMUNICATION 57 
NATURA SLOVENIAE 25(2): 53-60 
 
Figure 2. Distribution of broad-bodied chaser Libellula depressa and blue chaser L. fulva in Slovenia, with indicated 
localities of syntopic occurrences of both species (source: database of the Slovene Dragonfly Society and the Centre for 
Cartography of Fauna and Flora, October 2023) 
Slika 2. Razširjenost modrega ploščca Libellula depressa in črnega ploščca L. fulva v Sloveniji, z označenimi lokalitetami 
sintopičnega pojavljanja obeh vrst (vir: podatkovna zbirka Slovenskega odonatološkega društva in Centra za 
kartografijo favne in flore, oktober 2023)  
 
As for the observations of mating activity of both species, considering conspecific pairs with 
copula or tandem formation, the above-mentioned database contains 164 data for L. depressa 
and 147 for L. fulva, but with an inverse ratio of only 220 individual conspecific pairs observed 
in the former and 471 pairs observed in the latter. Regardless of the commonness of L. depressa, 
the above numbers are not surprising due to the different mating behaviour. In L. fulva, 
copulation usually lasts between 10–15 minutes, with the pair usually settling in a sunny place 
after a short zigzag flight, while in L. depressa, copula formation is very short and copulation 
completed in flight usually lasts only 4–30 seconds (Sternberg 2000; Sternberg et al. 2000; 
Wildermuth & Martens 2019). However, the presented data from Slovenia show that the 
observations of conspecific mating attempts extracted from all faunistic data of the species are 
not rare, but nevertheless much more frequent in L. fulva (15.7 %) than in L. depressa (4.4 %). 
  
Other factors that may have contributed to the rare anomalous mating attempt are the 
specifics of the microlocality, where the road bridge and overgrown upstream section direct the 
adult dragonflies to concentrate around a small shallow pool and stream section with some open 
water surface only a few square meters in size. In such small-size environment, conspecific and 
heterospecific interactions are more likely to occur. It should also be noted that the end of June 
falls towards the end of flight period for both species, which means that the individuals are 

58 Matjaž BEDJANIČ: Observation of heterospecific mating attempt by blue chaser ... / SHORT COMMUNICATION 
NATURA SLOVENIAE 25(2): 53-60 
a l r e a d y o l d , a n d h a v e m u c h l e s s v i v i d c o l o u r p a t t e r n s , a s e v i d e n t f r o m t h e d u l l b r o w n i s h 
coloration of the L. depressa female, which has also developed a slight light blue pruinescence 
on the dorsum of the middle abdominal segments (Fig. 1b). Neglecting considerably broader 
abdomen and the larger dark basal spots on the fore and hind wings, this colouration somewhat 
resembles the colouration of old L. fulva females and may have contributed to the observed 
mating confusion. 
 
As the Slovenian odonatological records clearly show, it is obvious that L. fulva and  
L. depressa occur together spatially and temporally and that they often share the same habitats 
at the same time. The situation is probably similar in many other parts of their range in Central 
Europe at least. It is therefore surprising that the present observation is only the first evidence 
of an anomalous mating attempt with copula formation between the species involved. In the 
present case, the locality specifics and the older age colouration of the involved L. depressa 
female could have been the decisive factors. In any case, the complete lack of similar reports 
from elsewhere suggests that the mate recognition and other mechanisms that prevent 
heterospecific mating attempts between the two species are apparently very effective. 
 
 
 
Povzetek 
 
 
Poročila o heterospecifičnih poskusih parjenja pri kačjih pastirjih niso skrajno redka (Bick & Bick 1981; 
Utzeri & Belfiore 1990; Corbet 1999). Tudi znotraj družine ploščcev (Libellulidae) so bili poskusi 
heterospecifičnega parjenja, ki so posledica napačne prepoznave samice s strani samca, opazovani že 
velikokrat (npr. Bick & Bick 1981; Rehfeldt 1993; Wildermuth 2015; Kornová et al. 2022; Chovanec 2022). 
Velika večina poročil pa temelji le na opazovanjih tandemov samca in samice, brez dejanske kopulacije. 
Opazovanja heterospecifičnih paritvenih kolesljev so mnogo redkejša (npr. Kunz 2010). Za vrste ploščcev 
(Libellula spp.), ki se pojavljajo v Evropi, je znanih le nekaj primerov heterospecifične kopulacije  
(npr. Seggewiße 2008; Wildermuth & Martens 2019). V pričujočem članku je predstavljeno opazovanje 
heterospecifične kopulacije med samcem črnega ploščca L. fulva in samico modrega ploščca L. depressa,  
o čemer v literaturi še ni bilo poročil. 
 
Konec junija 2022 je bila ob manjšem potočku v območju Natura 2000 Ličenca pri Poljčanah v 
severovzhodni Sloveniji prvič fotografirana uspešna formacija paritvenega koleslja omenjenih vrst  
(Sl. 1a–d). Samec črnega ploščca in samica modrega ploščca sta po nemirnem spreletavanju v tandemu 
prvič oblikovala paritveni koleselj le za nekaj sekund (Sl. 1a), po razpadu katerega sta ostala v tandemu  
(Sl. 1b) in vnovič tvorila paritveni koleselj za poldrugo minuto (Sl. 1c, d), potem pa odletela in ju ni bilo več 
na spregled. 
 
Sočasno pojavljanje odraslih kačjih pastirjev v prostoru in času je predpogoj za morebitno 
heterospecifično spolno interakcijo. Predstavljena razširjenost črnega in modrega ploščca v Sloveniji (Sl. 2) 
kaže na številna prostorsko prekrivajoča se opazovanja. Podobno velja tudi za časovni vidik – obe vrsti sta 
bili zabeleženi hkrati na isti datum na 279 lokalitetah, za katere je znanih 375 favnističnih podatkov.  
K opisanemu redkemu poskusu heterospecifičnega parjenja so morda prispevali tudi specifični dejavniki na 
majhnem zaraščenem odseku potočka z le nekaj odprte vodne površine. Podobno velja za obarvanost 
postarane samice modrega ploščca (Sl. 1b), ki je kljub znatno širšemu zadku in večjim temnim lisam na bazi 
sprednjih in zadnjih kril, s prevladujočo rjavkasto obarvanostjo in rahlim sivkastim voskastim poprhom na 
zadku, nekoliko spominjala na obarvanost starih samic črnega ploščca. 
 

Matjaž BEDJANIČ: Observation of heterospecific mating attempt by blue chaser ... / SHORT COMMUNICATION 59 
NATURA SLOVENIAE 25(2): 53-60 
Glede na pogostost črnega in modrega ploščca v Sloveniji in Evropi preseneča, da poskusi 
heterospecifičnega parjenja med njima doslej še niso bili zabeleženi. Ustrezno prepoznavanje potencialnih 
paritvenih partnerjev in drugi mehanizmi, ki preprečujejo heterospecifične poskuse parjenja, so pri obeh 
vpletenih vrstah očitno zelo učinkoviti. 
 
 
 
Acknowledgements 
 
 
Thanks are due to Martin Schorr (Zerf, Germany) for help with literature. Ali Šalamun (Ljubljana, Slovenia) kindly 
produced the map, helped with information on faunistic data from the odonatological database of the Slovene Dragonfly 
Society and the Centre for Cartography of Fauna and Flora and discussed on parts of the manuscript. Thanks to the reviewer 
for the analysis of the manuscript and constructive comments. The preparation of this article was funded by the Slovenian 
Research and Innovation Agency (the research core funding No. P1-0255). 
 
 
 
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