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Hi everyone

I wanted to ask which families or species of insects would be best suited as biodiversity indicators, for a variety of habitats. Also, which counting method is best to determine the number of individuals in the field? Another question is regarding the minimal number of trips one should make to the desired place to count (I wanted to know if anyone has any suggestion). Sorry if I?m sounding like I?m pushing for an answer, but this is kind of urgent, so fast answers will be greatly appreciated!

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Beetles seem to be used a lot for this sort of study. Flies would be good too, but there seem to be fewer studies using them.

You need to employ several methods of trapping to ensure you get the widest range of species. It is virtually impossible to come up with meaningful quantitative population figures for a species - you can really only give numbers of a species caught in relation to total numbers of individuals caught. It is possible to express an opinion of a species status based on your own and past records, but with many species it can be little more than a guess.

Some useful literature:
Environmental Monitorying, Surveillance and Conservation using Invertebrates - M Eyre (ed) 1996, Newcastle, EMS Publications - lots of good stuff, but some outdated. A series of case studies - some published elsewhere also.

Ecological Census Techniques: a handbook - W Sutherland (ed) 1996, Cambridge, CUP.

Handbook of Biodiversity Methods: Survey, Evaluation and Monitoring - D Hill et al, 2005, CUP

Invertebrate Surveys for Conservation - T New, 1998, Oxford, OUP.

Fowles, Alexander and Key - The Saproxylic Quality Index: evaluating wooded habitats for the conservation of dead-wood Coleoptera - The Coleopterist 8(3), 121-141

Quantification of Conservation Criteria using invertebrates - M Eyre and S Rushton, 1989, Biological Conservation 26, 159-171

I think the minimum number of trips is 3, timed to peak periods throughout the year eg May, July and Sept/Oct. It isn't really enough, but it is a start and will give you a reasonable range of species, and provides a stepping stone for someone who comes after. To make the study really worthwhile you need to be able to return year after year.

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Thank you so much for your quick and excellent answer Susan. I'll check those books, see if I can get them.

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to add something.
butterfly are again very used, and some day butterfly/moth are more or less easy to quantify as number (capture/marking/recapture and or pheromone).

and also dragonfly, on this very good quantitative studies can be done but specially based on larva/exuvia (when is about aquatic habitat) on adult capture/marking/recapture.

and one last thing: from the very few i know about south: another biodiversity peak is somewhere like february/march.

cosmln

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Hi cosmln,

Thanks for the extra info. I think your information will be very useful.

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To have to test these studies on various types of forest in Belgium, we could draw little from conclusions!
It is necessary to badly test not goupes with various traps and the results vary from one year to another!
The methods is analyzed appear unsuited the ones after the others to the wire of time!
More serious, in fact always the same groups are used as objects of study to characterize a site!
To have to test on of Geotrupes the system marking with crammed traps of droppings, that does not give valid indications!

Nothing is worth the sense of smell of an old entomologist to appreciate a site and its biodiversity!

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Both dragonflies and butterflies have the advantage that they are small manageable groups of species, but they may have the disadvantage of not being relevant to all your habitat types.

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Thanks! I will use some different groups like Diptera, Lepidoptera, Coleoptera, etc. The work will be a sort of a test to see how it works. This was kind of urgent because I had to have a general outline by today.

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Could you explain how does a Malaise trap work? What I want to know is whether the ten gets set during the whole biodiversity peak, or for less time. Another thing rattling my mind is what to do with the enormous ammount of insects one in theory catches is this kind of trap. I'll be choosing some groups for study, but what should I do with the other insects? To those of you who have already used this method, what do you do with insects that are not of interest?

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Hi Rui,

here: http://www.entomo...e_trap.htm you can read how a Malaise trap is working.
hope this helps.
you have also a PM.

cosmln

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Thanks so much for your help cosmln, this helps a lot.

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Rui - you have hit upon one of the great disadvantages of malaise traps and the main reason I don't use one. Malaise traps really need a team of people and an individual with plenty of time because of the quantity of material. I am more and more careful to limit my catch to what I have time to deal with, but I am doing this in my more and more limited 'spare' time. The disadvantage for the site is that there are many species I will never pick up using just a net and pooter, but there is no diptera inventory (except for syrphidae) for the site I am working on now, so c'est d?j? ?a

I would suggest pan traps are quite good for small scale diptera surveys, being cheap and easy to manage, if you want to go beyond just netting, but still have limited time.

The two other reasons I have never used a malaise is the expense and I was previously surveying a site where it would have been vandalised and I am now surveying a site that I can't get to regularly enough to check the trap (although hopefully that will change in the next year or so).

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One has to be innovative! No reason to "bad mouth" Malaise traps simply because they are usually used to collect and kill insects. Simply change the collecting head from a killing jar to a larger cage, or block off the entrance to the killing/collecting jar. Most insects are 'quite happy' to stay alive in the trap (not actually happy but they do eventually come to rest at the top of the trap).
Vandalism can be a big problem but when I collect tabanids with my Tent Traps (essentially 'flight interceptor traps', as is a Malaise Trap) I use them for a couple of hours in the area. I then collect in the area with a standard insect net. Invariably the Tent Trap collects at least 10x as many tabanids as I get with a hand net; it also collects many more other insects that I catch with a net. In fact it usually catches so many insects that I don't have time to collect outside the trap, kept too busy selecting tabanids from the trap.
So, use a Flight Interceptor trap to trap flies, remove those you want and at the end of the day release all the insects.
Some discussion on traps:
HERE
Some of these new tent traps are 'pop-up' tents and can be set-up in less than 1 minute.

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Tony - I was hoping you would step in here and be innovative

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Wow, thank you guys for the input. Maybe I'll quit the malaise traps because for now I'm the only person that will take the responsability to deal with the insects. And there isn't just one site, but five.
I'm thinking of using some families of Coleoptera, Diptera, Odonata, Hymenoptera and Lepidoptera....I hope that it isn't too much for just one person.
As new questions arise, I'll be asking for your help.

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Rui, can you tell us what you are trying to achieve. Do your objectives really require quantitative survey? There is a huge difference between quantitative and qualitative surveys, the former require considerable care and rigour, lots of duplicate samples, ideally over several years to overcome all the variables out there in the "wild". Really, to do it properly, it is a PhD project.

Even if you do all this, and get a result, how will you interpret it? Any threshold diversity/ abundance indices there might be would not necessarily be valid in Portugal.

If all you want is a quality assessment of a site then a qualitative survey will do, but even here you need other sites in Iberia that have been assessed using the same techniques with which to compare.

In GB such qualitative assessments are done by producing a species list (min 100 species, 200-300 better) then applying species quality grades to all species. One can then come up with an assessment based on a comparison with known high quality sites. In Portugal I doubt if such species grading or previously assessed sites exist.

The best indicators depend on habitat, basically parasitoides and predators and dead-wood specialists are most sensitive to habitat disruption so (in GB at least) a good list of these will indicate a high quality site. Least good are phytophages and highly mobile species (so butterflies not very good, but are used because the ease of identification together with an army of amateur recorders means you can get large datasets and good ecological knowledge of them allows one to understand results better). I am biased but I really think Diptera plus aculeate Hymenoptera provide the best ecological coverage, there are almost no ways an insect can live which is not found in these groups. Also both can be sampled with a sweep-net and in the case of Diptera, large samples can be obtained in a short time. Beetles are very useful but it is impossible to get such a large sample in the same time without using diverse trapping techniques, which makes a survey so much more complex.

In conclusion, unless you have tens of thousands of euros to play with, do a minimum of three field trip days, May, June and August (but in Portugal I suspect April, early June and September would be better), sample selected Diptera (depending on habitat and identifiability) and aculeate hymenoptera.

Hope this helps.

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Are Diversity Indices out of favour? I used these to compare sites for moth diversity several years ago.
See Here for an overview

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Horses for courses, they never were in favour with me because diversity is not very important in my habitat assesment work. Site A with 100 common, widespread species is more diverse than site B with 50 species but if 20 of these 50 are rare and endangered then site B is the one which needs to be identified as of conservation concern. Indeed low diversity sites are often the best places for scarce species, early pioneer communities being a prime example.

So its all about what you are trying to find out about the site.

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The work's goal is to create a numerical classification of the diversity one can find on a given place (I was contacted to collect and to try to identify insects). David, when you say ?do a minimum of three field trip days? do you mean 3 days in each month, or 3 days during that 3 month period (1 day in each month)? Another thing, how do you use sweep netting in a study of this kind? Do you do a fixed number of sweeps in a given route, or do you actively capture the specimen of interest?



Yes Tony, I believe that is the final goal of the work (I'm not directing it, I just capture and try to identify the insects, as I've said)

Regarding the dipterans, I'll almost surely use Tachinidae, maybe Bombyliidae as well, given these are also parasitoids. I still have to give more thought to which families I'll use, but I think the ideal would be to choose a small number of them. I'm just going to choose the ones that are of extreme importance to the study. Thanks a lot to both of you for more of this precious help.

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David :It is what I think but expressed well better!