I feel like I don't know anything (but that's alright)

A barkfly. Who'd have thought it. CC image S. Rae

 This morning I have been decanting some Tullgren funnel samples into pots for another class. I'm never fully convinced by whether they work, and also the leaf litter that was collected for them was pretty crispy - so the pots aren't exactly overflowing with creatures. But even so, I've spotted things in there that are going to make me look ignorant if someone asks me what they are.

Last year I spent a considerable amount of time swotting up about little soil creatures and making a guide: I learnt about things I had no idea existed (Protura, Symphyla) and realised I knew close to nothing about the groups I did recognise (Millipedes, Centipedes). And then today I ruefully realised that there are many many more things I don't know about that might be in those pots (Barkflies, Thrips... who knows) and I'm not going to become an expert before next week's class. Much as I'd like to be, for the students' sake as well as my own.

But this is not a reason to give up, is it. It's a reason to start. The world is full of amazing things. You can go and look for them and dip your toe into understanding how the world works. Knowing what's out there and where it is, underpins any scientific research in ecology and conservation.

Polyxenus lagurus, a perfectly common UK millipede. Who knew. CC image Andy Murray.

I also find it quite good for existential angst, as all those plants and creatures are out there doing their thing regardless. That's quite reassuring when you get depressed by the absurdity of your own species (from international politics, to celebrity 'culture', to daft things happening in your own social sphere, to your own behaviour).

So my point is, don't be daunted by feeling you don't know anything at the start of this assignment. Ok, maybe some people know a little. You might fear they know a lot. But it's not a 'zero sum game' as they say - their knowledge isn't going to make yours less, and in fact I can tell you from experience that people are very generous in sharing their skills. Pick something you think you'll find interesting, and dive in. Rome wasn't built in a day (and all that). Remember that all those admirable experts started with a single beetle, or wild flower, or barkfly, once upon a time. Begin now.

Charles Darwin age 7. Painted by Ellen Sharples in 1816.

P.S. A ridiculous and authentic post script.
I spent some of the lesson staring down a microscope with student J, trying to work out what the tiny 4-winged, long-antennaed creature in the petri dish was. In retrospect I think it was a bark fly, though this definitely didn't occur to me at the time. It's a shame isn't it. I can only trust that your young flexible brains will cotton on to things much faster. Here's a gallery of them so I don't get confused next time.

What a great day for football: all we need is some green grass and a ball.

CC image Rune Mathison / Bitjungle

I can't lie, I have no interest in football at all, but as it's the start of the world cup here's a topical Grass/Football quote for you from Bill Shankly. I discovered I was right in imagining most pitches use the ubiquitous dark green species Lolium perenne (Perennial ryegrass) - but I've been interested to learn that big grounds use an space-age interwoven hybrid of actual grass and artificial fibres. I know, you learn a new thing every day.

I'm now pleased to have 22 species of grass, virtually all from mundane, easily accessible habitats - imagine the variety if you went out and about. It being June I am aware virtually nobody is reading this, which is a shame as I wish I could persuade you to try collecting them too. Yesterday I went to the wood/grassland you much-frequented in your first year and found a few more. I'm still remarkably confused about a couple, but the more I look at, I think the more likely I'll realise what the mystery ones really are (and to realise if I've identified things incorrectly in the past). It starts making me wonder how my brain is picking this up - some of it must be rote learning and repetition, but there's an element of recognising and comparing little characteristics to those of species I already know. No doubt a psychology student could tell you more. I can feel strange things happening in my brain but I'm not sure what they are :)

I found the rather elegant Remote sedge (with spaced-out flowers and long terminal bract). CC image by P Verstichel.

 I was roaming the grassland because one of the lecturers wants an NVC (National Vegetation Classification) category for it: a method you may learn in your future classes. About half the species I found were grasses, and they're essential for an accurate NVC. So if you get good at identifying them, an ecological consultancy would probably be highly impressed at your usefulness (though the adverts I see seem to be obsessed with newts and bats - not that I don't like such charismatic creatures, but the law is highly species-ist, grrr).

Now I must attend to my new specimens and get them pressing.

Plant Detective

I deduce these are actually plastic leaves. Public Domain image.

 Sometimes people send me and Dave photos of mystery plants hoping we'll be able to identify them. Today's email from a student was marked "With High Importance" which made me inwardly groan a little bit. But actually I relish the challenge so I set about looking for clues.

It made me think of the importance of you recording good information in your Field Notebook - out in the field. Some things are really useful to note, and if you forget to, not only might you lose marks, but you're making your life difficult when it comes to identifying your specimens later.

It's a very good thing to take a photo of your specimen in situ - I would feel smug if I ever remembered to do such a thing on one of my lunchtime strolls (I haven't). But it can be hard to capture the habitat with a mere snap. Today's student's blurry plant might have been from the Mint Family (Lamiaceae) - I could just about make out a square furry stem amongst its opposite leaves. But to know whether it was in a damp habitat or a dry one would have been useful - I could have ruled out a number of possible species.  So it's really good if you can describe the habitat in your notebook - what other plants are around? Is it amongst rocks, or in a meadow, or next to a stream, or on the seashore? That would have helped me a lot, and could help you.

Plant with scale (insects, that is). Sorry. CC Gilles San Martin.

 The other thing that irritated me about the photos could have usefully been included was some indication of scale: just putting a pencil or foot in shot gives you a clue to the size of the leaves or other features.

Not always relevant (but sometimes very important) is your sense of smell. Plant-squeezing is one of my go-to clue-finding methods. A mint would be immediately obvious but many plants and flowers smell distinctive. So do some mushrooms (e.g. the ever memorable descriptions of  'wet washing' and 'crab' for certain Russulas). Even some insects exude strong smells which you might later find mentioned in an i-d book.

With "ordinary" plants my first stop is their flowers, and then to look at the shape of the leaves and the pattern they attach to the stem. I read this interesting article by Catherine Stewart describing her own process of identifying mystery plants. But with your own group you'll soon begin to realise their good early diagnostic features. Maybe that'll be behaviour for spiders (is it running across the ground or sitting in a web), or pinnateness for ferns, or general proportions for a snail, or type of fruiting body for a lichen.

This Oil beetle's kinky antennae are a clue to its species. But as with my own photo, there's not enough detail to be sure. CC0 image.

You'll be bringing your specimens home so don't have to worry to much about taking a super clear photo with every detail. Good photos and notes are even more important if you can't. The other week my sister and I found some amazing Oil beetles while out for a walk. I insisted she take some photos so we could report the sighting (there is a dedicated website you know), but I'd forgotten what the beetles' most important features were - so it turned out when I got home that the very bit of the beetle that needed to be in focus was the bit that was blurry. Well, you live and learn.

So when you're out and about collecting, really do take your notebook and note down some clues. Are those lichens only happy on the top of the wall? Are those snails anywhere else but on the tree trunks? Is that grass suspiciously present where dogs wee? (that'll be Wall barley then). Am I repeatedly seeing this seaweed at the same point up the beach? Observations. Think like a detective. You won't remember all this stuff unless you write it down. And the people marking your notebook will love to see it. Every year I read their plaintive calls for field notebooks written actually in the field. They will be desperate to give you some extra marks.

Wall barley (Hordeum murinum) in typically unsalubrious location. CC Stefan Iefnaer.

Gratifyingly, today's Student-with-mystery-plants has just emailed to call me a "bloody miracle worker" for my identifications (let's just hope I'm right).

Using Vernier calipers

You might recognise the contraption above as my self-designed Limpet Height Measurers from your first year trip to Dartmoor (patent still pending). But I also often thrust them upon people who are collecting snails, spiders, beetles and so on, because trying to measure these creatures can be a lot easier with Vernier callipers than grappling with a ruler. Sometimes that's because rulers don't easily fit in petri dishes, or because 3D objects don't easily sit against a ruler, or just because it saves you holding something small and fiddly while trying to squint at a tiny scale at the same time.

The distances between the red arrows above are all the same, though mostly you'll probably be using the bottom left gap (for snail width or spider body length for example). Most of the time you probably won't need the precision of the Vernier scale at all - millimeters being good enough for most things of this nature, but here's a quick reminder of the whole process.

Being a proper scientist you'll be working in mm or cm not inches, so use the scale on the lower side of the calipers. You want to read your distance off against the line above the O (some people get confused and want to read where the gap of the jaws ends).

So this is somewhere between 1.7 and 1.8cm (17 and 18mm), would you agree? That might be good enough for your purposes (if the question in your key is 'Over 15mm or Under 15mm, for example).

But if you did want to know how many bit-ths of a millimeter it was, you must now forget the main scale and scrutinise the 0, 1, 2, 3 etc Vernier scale.

You ask yourself, which of the lines in that scale matches up in a straight line with one of the lines above it? I would say all the ones at either end are quite askew, but the best choice is at 5 and a half - yes?

So that means after our aforemeasured 17mm, there is 0.55 more of a millimeter, making 17.55mm in total.

That would be a bit over the top for most things, but with some groups you might get a key that requires you to know the measurement to the nearest 0.5 of a millimeter (for example, the descriptions of sedges that I was looking at yesterday talk about the leaves being 1.5-2 mm wide, or the fruits being 3.5 to 5mm long).

 There are of course digital Vernier calipers these days, but I ask you, Where is the Fun in That? You wouldn't know if they were lying to you or not. Likewise their batteries are apt to die at the most inopportune moment (and they are always some obscure size of watch battery that you haven't got). It probably seems strange for a technician to be a Luddite (maybe I need to speak to a therapist). But I maintain this is borne of bitter experience: simplicity is often better. Besides, you will learn a skill which you can take satisfaction in. Here endeth the sermon. If you'd like to borrow some calipers do come and ask. I might even lend you the digital ones if you want.

CC image by Lookang

(If you want to know how a Vernier scale works, and who wouldn't, you could do worse than reading this anonymous blogger's website.  Mr Vernier himself was a French mathematician that lived c.1600.)

Keep Off The Grass

Phleum grasses are distinctive for their ROCK horns. CC Matt Lavin and AJC1.

 This is a funny time of year in my job. Most students have disappeared and I have time to do some of the interesting things that fall by the wayside during term-time. But it takes adjustment to get used to the freedom, and I actually find the campus a bit depressing when it's so quiet. So instead of sitting at my desk eating seaweed (my latest exotic find in the SU shop) I have been trying to maintain liveliness by going for a walk at lunchtime.

I took a plastic bag today for collecting things. Taxonomic collection rule number 1: Always have your bag or pot. I saw lots of grasses. They're probably responsible for all this sneezing going on at the moment so I considered it revenge to pick them. This is a great time of year for a grass collection since they're in flower - you certainly don't want to do yourself in by trying to identify them without their flowers.

Taxonomic collection rule number 2: Ignore everybody else. I was standing motionless staring into a big bed of wildflowers, looking for grasses. A student walked near me singing to himself - then he clocked me and presumably felt embarrassed for himself, and also maybe bemused for me because I looked quite strange standing there clutching my plastic bag of vegetation. "All right?" (he had to repeat this as I usually expect my strange aspect to deter communication). "Yes, I'm all right? Are you all right?" "Yes." It made me laugh anyway. So definitely don't worry about looking weird. If anybody's actually paying attention they'll probably be too awkward to ask you what you're doing anyway.

Old skool botanising, same as it ever was. CC Wellcome Images.

So get this - I found 16 species of grasses (Poaceae family) just wandering round campus. I was surprised there were so many. Imagine the marvellousness of your collection if you started grasses now, and went to different habitats and collected even more. It would have the potential to be truly marvellous wouldn't it. Well, I would be impressed at least.

I brought my haul back to the lab and was pleasantly surprised at how many I knew. Maybe this knowledge has been seeping into me slowly over the years. You see, there is hope even with apparently off-putting groups like grasses. Like anything, if you get to know the common species, you'll naturally begin to spot when something's odd and different.

And if you're in a particular habitat, there will be a certain range of species you're likely to find, which helps with identification too. I was on the MSc field trip last week to Steart Marshes, which has lots of developing salt marsh. I brought back two special salt marsh species from there (though there were more... collecting just wasn't on the top of my mind).

Botanists pressing plants in the field - yeah fine in Mexico where it doesn't rain :) CC Alan Harper.

I've pressed my finds and I'm hoping to mount them - but I'm in a good position because I already know what I'm looking at. If you've collected grasses you really want to identify them while they're still fresh, because their identification features include membranous ligules and leaf width - things that will unhelpfully shrivel when pressed. You can keep your finds in a plastic bag for a while in the fridge until you've sorted them out.

It would also be really useful to take photos or sketches of your plants in the field, as the "look" of grasses can be quite distinctive when they're en masse - sometimes they look much more shimmery or brightly coloured in the field, and that can help with identification.

If grasses take your fancy this fold-out guide is a good and cheap start. I have found Francis Rose's 'Grasses, Rushes and Ferns' the best book - it has detailed illustrations of the spikelets. The latter is super expensive, so do come and borrow one from me. It's too heavy really to carry around though, but I have had much success with Dominic Price's recent 'Field guide to grasses, sedges and rushes', which includes excellent identification Top Tips and lists for particular habitats - I'd recommend it very much.

Nice ligule. CC image by Harry Rose.

Anyway please do ask for for a bit of help if you wish, as it's useful to get some feedback from someone who knows a few species for sure.

Identification thoughts

A lichen from yesterday, Hypogymnia physodes, and its weird inflated catpaw lobes. CC image James Lindsey.

I had a nice afternoon yesterday with student T and her extensive lichen collection. We were using a combination of guides and keys and a bit of my prior familiarity with their appearance. It made me think of two things. Firstly, that it's always a good idea to use more than one source of identification. I do love the FSC but even they can't squash everything onto a fold-out guide - lichens are great when they look like they're supposed to, but sometimes they just don't. You might think that's because they're a totally different species and I just can't identify them. But it's not always that. It's because many of them are annoyingly variable. If you went on KL's lichen jaunt around campus the other week, you'll have seen my attempt to make a guide that includes half-eaten lichens as well as pristine ones. It's not even nibbling that's the main problem though - sometimes the lichens look different just because of varying conditions where they're growing (or possibly they do it just because they feel like it, who knows). So, point one, whatever you're collecting, it helps to have a variety of (reliable) descriptions and photos. Hopefully I've given you a few options for your own group in this blog, but I'll keep looking.

Secondly, lots of people have limited transport, so only collect their lichens where they can get to around Bristol. This has the effect of making me look cleverer than I am, because the species they turn up with are generally on a relatively limited list. Nitrogen dioxide and other pollutants limit which can live in the city. So point two, if you can obtain an idea of what you're expecting, it can help. For lichens, the FSC fold-out guides are habitat based (eg urban, heaths, seaside) which is great. And when we were doing the mosses the other day, there were lists at the back of the book for different habitats (it's also online). This is useful as an additional identification strategy (especially with groups where there are many many species in this country).

Spider eyes and ID

I've recently returned from the expedition to Cuba. And guess what I did there... I held a tarantula. I'm very proud of this. I feel that spiders and I are now better friends. It wasn't ENORMOUS but it was a good handful. I liked it so much that I insisted on holding it three times. In the end it relaxed quietly in my palm while I casually spoke to people. So this new familiarity helped me the other day when Student A arrived to identify his specimens (any spider looks like tarantula under a microscope so it's best to be prepared).

Wolf spider by Thomas Shahan

We found the main dichotomous keys difficult. It would have been better if we could have turned to an expert arachnologist to explain what was being got at. But as lone neophytes we found the lateral key in the Aidgap spider families key the best place to start. To avoid tears you may want to do the same. After finding a likely family we then went to the Collins Guide.

I learned three important things. Firstly, that a pickled spider may be helpful because it's still, but otherwise it's an alive spider that can tell you many more useful things, and you should have written those things down when you found it. Identification will be greatly more likely if you can authoritatively say something about a spider's habitat, behaviour and web or lack thereof - all these things feature in the keys.

Secondly, that the arrangement of a spider's eyes is very useful in its identification, -  this would be a critical thing to observe and draw in your notebook.. The wolf spider above has two big headlight-style eyes at the front, two offset towards the back, and a curious row of four small eyes below - just like the wolf spider Student A found. Doubtless the big front eyes are an adaptation for seeking out prey. But what's going on with those four small eyes? I feel like i want to know more about spider eyes. I'm not sure that's something you hear every day. But do most people even know that most spiders have eight eyes?

Thirdly, it's very likely that you're only going to be able to get so far with the keys - distinguishing species usually comes down to very careful observation of the reproductive bits of adult spiders. That feels like pretty advanced stuff and on small specimens such things might be too difficult to see at all. I felt we could discount some options on grounds of habitat / geography / rareness instead. But often we were still left with a choice and it would have been dishonest to pick one over another. I think you need to make clear in your notebook your decision making process for either stopping at the Genus, or pressing on to a particular Species. Spiders just are difficult. I think the person marking your collection will have to acknowledge this.

Image by Hans Hillewaert

This is Dysdera crocata, the woodlouse-eating spider, one of A's finds. We were able to name it to species level because of its size - ours was female with a body of 15mm, so could only be the species crocata. This was a satisfying moment after all the previous pain. Dysdera has (apparently) only six eyes - they look like this:

Image by Patrick Moran.

We were also caught up in looking for cribellums and calamistrums - the lovely words of the new terminology amused me even if we had difficulty finding the things. I'm quite sure though that the more spiders I look at, the clearer all these things will become. It just takes effort and time. (Which is why you shouldn't leave things until late. This is very late in case you were wondering.)

If you want spider-related reading, I've just found  Rod Crawford's Spider Myths -  much for the new spider fan to enjoy, and much of it touches on the difficulties of identification. You can see all his arachnologist gear and read about his collecting exploits here, too. Or you may prefer the blog of the Spiderlord, who is based in the UK. He's pretty annoyed about our eight-legged friends being misrepresented in the media.

Successes in beetle identification

Kidney spot ladybird, as seen in OJ16 this week. It's a beetle too. CC image by GailHampshire.

Yesterday afternoon, student B and I had a go at identifying some of her beetles. It really was a triumphant success and she kindly said she felt a lot more confident about the process. I had a very pleasant afternoon and I think we both felt the geeky satisfaction of tracking a specimen through the keys and coming out at the right answer.

However, I thought I would mention here that this was not a speedy process. I've done some beetle i.d. before and so I was able to explain the terminology as it came up, pointing out the different parts of the beetle's body and showing her the classic beetle dichotomy of Crossed vs. Uncrossed Epipleura. So this speeded things up for her. But in three hours we identified three specimens. Yes this included faffing about finding microscopes, pins, printing off keys and chatting about other things. But you should still be aware that (at least to begin with) identifying your beetle (or spider for that matter) is going to take time. Do not leave things until the last minute.

Besides, we were enjoying the process, looking at the amazing detail of the beetles down the microscopes - they were surprisingly hairy, or stripey-lined, or with massive jaws, or with crazy antennae. So it was a pleasure to spend the time looking at them. Please do come and use the microscopes to examine your species, and I am only too happy to go through the identification with you. It's really useful to have two pairs of eyes to judge some of the characteristics.

We started off each time with Unwin's guide to families:

B's first specimen was huge, so much so that we initially tried to convince ourselves that the key was taking us towards the elbow-antennaed Lucanidae (stag beetles). But reason and logic prevailed. The short elytra (wing covers) led us to the Silphidae (burying beetles).

The extremely philanthropic Mike Hackston has an illustrated key to the Silphidae. And once we had got down to the right genus, his key for Nicrophorus led us to the answer: Nicrophorus humator. Fair enough, with a common species like this one, you might have been able to pick it out of the photos in a general insect guide. But you wouldn't have gleaned useful beetle-observing skills along the way and you might not have looked closely enough at the details that distinguish it from similar species.

CC image by Laisverobotams.

You'll see this species (the Black Sexton Beetle) has short elytra that don't cover the tip of its abdomen, and they look as though they've been cut off, straight across. It's got rather distinctive clubbed antennae too, and they're orange in contrast to the rest of its black body. We were rather taken by the furriness of the beetle's underside. This wasn't mentioned in the keys but we were wondering if it had something to do with the creature's lifestyle. This isn't a sweet little beetle with genteel habits. It's called a 'sexton' beetle because these seek out dead animals and bury them, laying eggs on the corpse. Some species eat fly larvae - and B found this example in a fly trap.

Our next specimen also had short elytra, showing even more abdomen. But its antennae were quite different. We used Unwin's key to put it in the Staphilinidae family - this contains about a quarter of British beetles! but luckily this species is very distinctive and we felt justified deferring to this excellent Watford Coleoptera Group page confirming its size makes it impossible to be anything other than the Devil's Coach Horse (Ocypus olens). It does seem beetles get all the best names.

The Devil's Horse Coach gets uppity. CC image by Galway Girl.

Finally we chose another black beetle from B's collection. It had long thready antennae, elytra that covered its whole abdomen, 'trochanters' underneath, and five tarsi on its front, middle and back legs. This made it a ground beetle - within the family Carabidae. Once again the keys generously provided by Mike Hackston were invaluable.  By steadily working through questions about the shape of its various parts, counting stripes and squinting for the existence of tiny hairs, we were at last able to confidently name it Pterostichus niger.

CC image by AfroBrazilian.

To the untrained eye little black ground beetles are pretty indistinguishable from each other. There simply isn't enough detail in a general insect spotting guide to be sure you've matched a species correctly - with beetles you have to be brave and attack the keys. But (as we did) you might find you enjoy it. You might get a little buzz out of solving the puzzle. And each time you do it, you'll get more familiar with the features you'll be looking for.

Naturally we recorded all we were looking at as we went along, drawing little sketches and writing down the reference numbers of the keys. Not only will this get you some marks for your notebook, it'll be a good reminder of all your previous beetles' features when you come to your next specimen.

A little note: you're welcome to come in whenever the university's open and sit in our lab. But just to say, I'm away on an exotic field trip for two weeks and will be back after Easter. I know. It's a hard job. And then you have three weeks to finish your collections. Let me know if you'd like my assistance and when.

Using keys

Dunno mate, looks like a wasp to me (actually the hoverfly Eupeodes corollae). CC image by Bas Lammers

 If you don't know what species a plant or animal is, there are various ways of trying to identify it:

You can make a wild stab in the dark (it's quick and doesn't require much effort - but you'll probably be wrong).

You can match its appearance to a picture in a book (this might work for something very distinctive, but pictures often don't show important diagnostic features, and most books don't usually have room to illustrate every species).

You can search the internet for something that looks like it, or ask in a forum (but you can't always be confident of the identification skills of random people).

You can ask an Expert (if you can find one, and they don't get fed up of doing your assignment for you).

Or you can use a key and gradually gain experience and expertise of your own in identifying the group it belongs to. This is more time consuming and requires some effort. But you'll be more likely to get to the correct answer.

Obviously I recommend the latter. Though there's a lot to be said for working with someone with more experience and picking their brain - they can highlight the most important features of your plant or creature. And it doesn't hurt to collaborate with someone who's collecting the same group as you either. You will get used the quirks of your key, but another pair of eyes and a second opinion can often help - and you'll help each other improve.

You'll see I've recommended some keys for each of the taxonomic groups. Various styles exist.

This one's a lateral key - use a strip of paper to mark the features of your own specimen, and compare it to the pattern made by the ones identified in the key:

With apologies to Sarah Whild. Our specimen (a custard cream) must be further down the list.

Lateral keys have an advantage in that you don't have to know every detail about your specimen (say if it's missing its fruit or antennae), or you mistake one of the features - you've still got a chance of matching most features and deducing an answer.

Most keys you'll see are dichotomous - they branch at each step and if you go the wrong way at any stage, you've had it. That's their disadvantage (especially if they're poorly worded or ask you about features you can't see). But a good dichotomous key will give you a selection of clear distinguishing features at each stage. Don't be downhearted if you find it difficult - depending on your taxonomic group, there may be a lot of terminology to get to grips with. But once you've struggled through the key a few times with different specimens, you'll be more confident about what it's trying to help you discern.

Once I know the sort of things the key asks, I find it really useful to start by making a little sketch of my plant or creature annotated with features I notice, or simply make a list. I find it makes it easier when I run it through the key. I'll try to make some pages illustrating this.

I won't rabbit on as the best way to understand your key is to use it - but if you're feeling brave I will just point out below that they can use different numbering systems. Don't feel scared by all the terminology - not all keys are so frightening and in any case I hope you may learn to love all those technical and specific words.

Most keys are set out like the beetle one below - you start by choosing between the pair of statements marked 1. and the "-" below the 1. Then you're given the number of the next pair of statements to read (either 2 or 6 in this case).

from Lindroth's carabid beetle key

An alternative is illustrated below. The pair of statements to compare are marked with the same number (1 and 1). You might also see 1a and 1b in some keys. Stace either gives the number of the next pair of statements to read (eg. 2), or sends you off to another key (eg. 2. Koenigia). A little more confusing perhaps.

from Stace's hallowed Flora

 But the most confusing in my eyes is the one below. You probably won't come across it because it's rather old-fashioned, but I've used it in my forays into identifying flies. The first statement is 1 (as usual) but you have to compare it with the number in brackets next to it (in this case, 4). So you end up having to look down (or even over) the page.

You'll notice that you're not given the number of the next statement to read. That's because you're expected to just move onto the next one. So if you agreed with statement 1, you move down to statement 2 (and its partner 3). Alternatively, if you agreed with statement 4, the next is 5 (and 6).

from Fonseca's key to families of flies

Anyway, I'm sure you'll be fine. But if you do have problems, just come and ask.