Hi Marcin,

I'm not sure the sex ratio of a whole family of beetles is a relevant piece of information.

Studies show that the sex ratio in Carabidae not only depends on the species but also on the period of the year and the environmental conditions (e.g. http://www.bjc.sggw.pl/arts/2012v12n2/452.pdf ). Even if someone had measured the sex ratio of every species of carabids everywhere on Earth and in every season, and pooled these data together, I guess that wouldn't help because the result wouldn't mean anything.

This is a very good question but I don't know the answer. Based on my experience, I always see a higher female to male ratio but I can't tell the statistical differences without analyzing them.

which reasons create that bias?

Good question Fernando but I don't know your answer too.

But then, how can you determine that the sampling method is biased towards one sex? can it just be a population without 50:50 male:female and thus the the method is just getting a random sample of individuals that are not 50%50 on sex?

Dear colegues

So bias in sex ratio in Barber trap results from different mobility of males and females (eg Szyszko et al 2004).

With regard to my question I tried find answer myself and now it seems to me that sex ratio in carabids should be 1:1. It was found to be such in soil/litter samples (e.g. Topping and Sundarland 1992) or amond hand-collected specimens (Mitchell 1963). The same was found in Pt oblongopunctatus and Cal melanocefalus in litter samples during long lasting studies of Jan Szyszko (Szyszko personal comments).

Additionally when sex is determined by sex chromosome (e. g., XY sex chromosomes), sex ratio is 1:1. Carabus have XY sex chromosomes (Weber 1966; Serrano & Galian 1998, Tsuchiya et al. 2012)

Just one more note on sex ratio in traps: sex bias results not only due to different mobility of sexes but also due to ability of males to escape from dry traps (Yamashita et al 2010; I think it should apply to some species which have males with modified tarsi). It does not concerns traps with killing preservatives.

I pulled these information so it might be of some use for some of you

Mitchell, B. (1963). Ecology of two Carabid beetles, Bembidion lampros (Herbst) and Trechus quadristriatus (Schrank). I. Life cycles and feeding behaviour. Journal of animal ecology, 32(2), 289-299.

Serrano, J. & Galián, J. 1998. A review of karyotypic evolution and phylogeny of carabid beetles (Coleoptera, Carabidae). In:Phylogeny and Classification of Caraboidea. (G.E. Ball, A. Casale & A. Vigna Taglianti, eds), pp. 191–228, Museo Regionale Scienze Naturali, Torino.

Szyszko J., Gryuntal S., Schwerk A. (2004) Differences in locomotory activity between male and female Carabus hortensis (Coleoptera: Carabidae) in a pine forest and a beech forest in relation to feeding state. Environmental entomology, 33: 1442-1446.

Topping, C. J., & Sunderland, K. D. (1992). Limitations to the use of pitfall traps in ecological studies exemplified by a study of spiders in a field of winter wheat. Journal of applied ecology, 485-491.

Tsuchiya, Y., Takami, Y., Okuzaki, Y., & Sota, T. (2012). Genetic differences and phenotypic plasticity in body size between high‐and low‐altitude populations of the ground beetle Carabus tosanus. Journal of evolutionary biology, 25(9), 1835-1842.

Weber, F. 1966. Beitrag zur Karyotypanalyse der Laufkäfergattung Carabus L. (Coleoptera). Chromosoma 18: 467–476.

Yamashita, H., Togashi, K., & Kiritani, K. (2010). Sex-related difference in the ability of Carabus lewisianus (Coleoptera: Carabidae) to escape from pitfall traps. The Canadian Entomologist, 142(06), 589-595.

Sorry to point this out again, but what does the sex ratio of such a huge family of beetles mean ?

no, no...

It was just a "shortcut". I was interested what is the real ratio since ratio in traps is biased. So I looked for some examples from field studies.

Great review Marcian

Great information on carabids! 

According to Marcin (based on his review), if sex ratio of carabids should be 1:1, then my experience says there is certainly a bias associated with the traps. I mean I mostly capture female but quite a few males.

I might have misunderstood the goals of your study, but I still don't understand what "sex ratio of carabids" means. This concept has no meaning if you consider more than one species at the same time, so the sex ratio of a huge family like carabids sounds really weird to me (especially if it's extrapolated from only a few species in the genus Carabus).

Vincent, apparently it is better write everything clearly. We are interested in the sex ratio of particular population at particular site eg population of Pt melanarius at one Baltic island. 

bye

Really nice discussion!

In my opinion we have very few information about sex ratio in carabids. Currently, I am working on sex ratio in three Nebria species living along an alpine glacier foreland. I collected them by pitfall traps. We analysed separately each species estimating (via bayesian approach) the detection probability of both male and female for each trap. Then we run the models to test the relationships between observed/estimated sex ratio and several covariates (e.g. epigean arthropods richness, vegetation cover, organic matter, time since deglaciation...), and the models were partialised always considering the detection probability for each sex in each species. We found very clear and interesting patterns, sinchronous for some species, but opposite for others. 

So, in my opinion pitfall traps can be considered a good method to evaluate the sex ratio, and sex ratio is clearly affected by some environmental variables. I hope to publish soon a paper on this topic : )

This is just what I think and what I found, but more species need to be tested with good statistical analysis. 

Bye! Mauro

Hi Marcin

We did some hand sampling in alluvial areas of Aare and Bünz. At each site we have cought Carabids in fourty parcels three time periods spring, summer, late summer, 20 minutes per parcel and time period.  See below the pooled species and the sex ratios. I will not test it yet but I guess the results endorse your 1:1 sex ratio for most species and the total too.

Art (lateinisch)

Male

Female

Acupalpus meridianus

1

2

Agonum micans 

6

8

Agonum muelleri 

12

19

Agonum sexpunctatum 

1

Agonum viduum 

2

4

Amara aenea 

12

15

Amara familiaris

1

Amara ovata 

5

5

Amara schimperi 

4

2

Amara similata 

3

1

Anchomenus dorsalis 

4

6

Anisodactylus signatus

3

1

Anisodactylus signatus 

4

3

Asaphidion pallipes

1

1

Badister lacertosus

1

Bembidion articulatum 

2

Bembidion ascendens 

7

20

Bembidion atrocaeruleum 

78

63

Bembidion decoratum 

1

1

Bembidion decorum 

52

46

Bembidion fasciolatum 

14

21

Bembidion femoratum 

46

44

Bembidion genei illigeri 

1

Bembidion lampros

3

2

Bembidion milleri 

1

Bembidion prasinum 

12

6

Bembidion properans  

9

5

Bembidion pseudascendens 

9

12

Bembidion punctulatum 

22

19

Bembidion pygmaeum 

1

Bembidion quadrimaculatum 

1

1

Bembidion schueppeli 

1

Bembidion semipunctatum 

1

2

Bembidion testaceum 

31

25

Bembidion tetracolum 

47

63

Bembidion tibiale 

1

Bembidion varicolor 

5

3

Brachinus explodens 

3

Bradycellus verbasci

1

Carabus granulatus 

1

Chlaenius tibialis 

8

7

Chlaenius vestitus 

4

5

Clivina collaris 

9

5

Clivina fossor 

2

2

Demetrias monostigma 

1

Diachromus germanus 

9

10

Elaphrus aureus

3

Harpalus affinis 

35

24

Harpalus distinguendus 

14

8

Harpalus luteicornis

1

Harpalus progrediens

1

Harpalus rubripes    

3

3

Harpalus rufipes 

4

8

Harpalus signaticornis 

1

1

Lionychus quadrillum 

41

42

Loricera pilicornis

4

2

Nebria brevicollis 

2

6

Nebria picicornis 

1

5

Notiophilus palustris

1

1

Oodes helopioides

1

Ophonus ardosiacus

3

2

Ophonus azureus 

9

6

Ophonus puncticeps

2

Oxypselaphus obscurus

1

Panagaeus cruxmajor 

2

2

Paranchus albipes 

30

25

Parophonus maculicornis

1

Patrobus atrorufus 

2

2

Platynus assimilis 

4

3

Poecilus cupreus 

8

13

Pterostichus anthracinus 

1

1

Pterostichus melanarius

1

1

Pterostichus nigrita

1

Pterostichus vernalis 

1

Stenolophus teutonus

8

8

T. parvula

4

4

Tachys bistriatus 

1

Tachys micros 

4

4

Tachyura quadrisignata 

59

67

Tachyura sexstriata

3

3

Thalassophilus longicornis

1

Trechus obtusus 

1

2

Trechus quadristriatus 

2

2

Trechus secalis 

1

2

Total

690

691

Very interesting, thanks for sharing !

Cool.  Thanks Thomas for the information

Dear Thomas,

thank you for sharing information. Please publish it , so not only RG readers could read it. 

Hi Marcin

thank you for encouraging me to publish it. I am preparing a publication entiteled "Habitat parameters and ground beetle assemblages in two alluvial areas in Switzerland - an approach based on hand-sampling" or similar and i used the data to do an overview of the carbids of the canton Aargau (Switzerland). The latter is in press now  "Zeitschrift der Schweizerischen Entomologischen Gesellschaft". Up to now I did not include the sex ratios, because I did not realize that it would be of much interest and there are only the mentioned two data sets (Bünz 2009, Aare 2009) where the identifiers distinguished between the sexes. May be I will do a short note for this journal, but I am not familiar with the literature dealing with sex ratios. Thus you might submit me literature informations or even better I could submit you the raw data and we may do the publication together or you may use the data for a review paper on the subject.

This is an interesting topic indeed...but does knowing the sex ratio in carabids help to answer any ecological questions?

Dear Marcin,

I'm not sure if you're still interested in this topic, but I recall a paper by Philip & Burgess (2008) where they used both pitfall trapping methods and active searches for Ctenognathus novaezelandiae. Pitfall catches favoured females (which is what I usually find for most Canadian species) wheras active searches of the forest floor heavily favoured males. Not sure if this is of use to you, but the article below may provide some evidence that information obtained from pitfall traps is skewed towards females, whereas alternative methods (active searches) actually show a more even sex ratio, or perhaps one heavily favouring males.

The article:

Philip, B. A. and E. P. J. Burgess (2008). Observations on the ecology and behaviour of Ctenognathus novaezelandiae (Fairmaire) (Coleoptera: Carabidae). New Zealand Entomologist

Dear All,

just few days and then I'll be happy to share with you a recent paper of mine in press on Ecological Modelling and entitled: Hierarchical meta-population models for describing space-for-time variations in insect population size and sex ratio along a primary succession. We considered three carabid species as model organisms and we discussed spatio-temporal variation in population size and sex ratio in relation to their detection probability in the pitfall traps and to some environmental variables.

Best, Mauro

Here is the link to the paper: http://authors.elsevier.com/a/1SjlO15DJ~lv35 cheers, Mauro

Thanks