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One thing to consider is the ease of identification / availibility of keys (or expertise) with the groups you choose.

Also, how much previous work has been carried out on them, if you catch a particular species can you give references as to its level of rarity or conservtion status for the country / region where the sample comes from. You may well be able to identify species but if there is no information as to the conservation status of the species then knowing you have "Species X" on site may not help you with an assesment of your site.

Personaly, I would not use Tachinidae as here in the UK many species would have to be classed as "Data Deficient", there is simply not enough information about their distribution to to qualify a list of Tachind species. Some we know about, others we do not.

Matt

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The problem in Portugal, Matt, is that we know very little about the species of almost every insect group. Choosing Tachinidae or other family is not different in that respect I believe.

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Perhaps something has been lost in translation but i do not understand this. sounds like a tautology to me, diversity is a numerical cassification.

It is, of course, utterly impossible to measure the absolute biodiversity of any site, thus any classification must be based on a sampled subset and only meanigful in comparison with other sites sampled in the same way. so the techniques used and the groups sampled are less important than is consisency of sampling between sites.

you say , but to what end?What are you going to want to do with this number once you have it? As mentioned in previous posts, diversity is not necesarily a measure of quality and without some baseline with which to compare will mean little.



I mean minimum of three days in total, however the more the better. I say three days because in GB this equates to a species list of 250+ which is an adequate data set, I would always like more but few clients will pay for more.



If you are doing a qualatative survey then your best approach is to use techniques which will produce the largeat species list in the most repeatable way.

Another thought, if mere diversity (rather than quality) is the index you want, then rather than target predators, parasitoides and specialists (most of which are low-density species), then saprophages, phytophages and the easily identified will give you max diversity for effort.

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Let us laugh a little!

To inventory the females of Andrena and the halictes, pitfalls should be put, for the females of Ichneumoninae too!
For the Cratichneumon genus, one takes the males out of yellow water vats or out of trap Malaise and the females with the trap of emergence.....pour Chalcididae, a rotatory trap to 35 m gives the best result!

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On the question of how many visits are needed, it might be worth looking at Chao's Estimator. It must be on the web somewhere. Once you have made a few collections, it predicts how many species are present in total. It is a simple calculation based on the number of species you have found only once and the number you have found more than once, though there are a lot of ifs and buts to take into account. The principle is: if there are lots of species you have found only once, there are probably still many present that you have not yet found at all.

John

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I've only had one informal meeting to try to outline the project. As such, I'm not very well into what I'll exactly do. Furthermore I don't have any previous experience of doing this kind of work, not even theoretical knowledge. I just have a general knowledge about insects and that's the reason I've been invited to help in this work.
So, I'm not yet in the position to clarify your questions. I'll have to meet the people who contacted me again to define the final objectives and from there on more correctly choose the insect groups and the sampling techniques.
Thank you David for raising these questions, now I know it's not as straightforward as I thought.

John, thanks so much for pointing me to the calculator, I think it will be a useful tool. I think you mean this:

http://www2.biolo...refact.php

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Rui:
You might find this software useful. Written by my son a few years ago. Not sure if it is still available.
Bio_Dap

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Great, thanks Tony. It seems the program is still available.

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Hi all,

As I have been planning my work on this survey several questions arose. I haven’t found answers for these specific questions. Is it possible for someone to shed some light on this, please?

1- Is bird predation a problem while using pan traps?
2- Do pan traps work in sandy ground? I'm asking this because I imagine that when there is much wind a lot of sand might get in the trap.
3- Will it be needed for the pan traps to be stuck to the ground or could they just be left on it? 10 meters apart from each other?
4- What I'm thinking of doing is set the traps in the early morning and then collect the insects in the afternoon, is that the right way to proceed? What is the minimum amount of time that the traps should be open each day?
5- The pan traps will be filled with a bit of salt and detergent. I know that the detergent must be unscented but is there any detergent that is more appropriate?
6- Should each pan trap be numbered?
7- As I mentioned above, I'll be dealing alone with many groups, each with many taxa involved. With your experience, do you believe I can deal with so many groups all by myself or should I limit myself to just some groups (dipterans or hymenopterans).
8- Which taxonomic level is more relevant? Obviously the species would be ideal, but many times it will be hard to identify.
9- I was told that one butterfly counting method is counting individual butterflies with an estimate of their relative density. I understand the basic principles but how is it really done, what are the necessary steps to be preformed? Do you have any literature on this?