Identifying invertebrates
insects, spiders and more
Identifying invertebrates is a hugely rewarding activity. Insects alone far (far!) outnumber vertebrates, both in terms of number of species and the sheer number of individuals. They are everywhere, living all kinds of lives. Add the spiders, and this diverse array of life is enough to keep even the keenest naturalist busy for a lifetime.
As must be evident from our website, we find invertebrates endlessly fascinating. And the importance of their roles in the ecology of the forest cannot be overstated.
However, identifying invertebrates does present particular challenges:
The limited Field Guides available
Field Guides are available for only some invertebrate groups. Such guides are valuable for identification to family and often to genus level. For some smaller groups there are even guides comprehensive to the level of individual species. We are fortunate that CSIRO continues to support the publication of such resources, regularly adding new titles on Australian invertebrates.
The many undescribed species
There are many species that have yet to be fully described scientifically. That is, they don’t have a scientific name and will generally not appear in field guides or identification keys.
Their small size
Many invertebrates are tiny, and the morphological differences between species are often only evident under a microscope.
Their individual variability
In some groups, there is considerable variation between individuals. Not only sex-specific or age differences, but also differences in size and colour depending upon their environment or conditions for growth and development.
Invertebrate anatomy has its own language
For people new to biology, there is a vocabulary to learn in order to make sense of even the simplest invertebrate descriptions. Fortunately, there are many resources to help – glossaries and diagrams, online and in field guides.
Tip 1 – Identification to family or genus is a worthwhile goal
For the reasons listed above, identification to species may not be possible, or may be impractical. Identification to genus, or even just family, can be enough to provide access to a wealth of information about the animal’s biology and ecology.
Observations and data
Photography
We find photography an indispensible tool for invertebrate species identification. It means we usually avoid the need to collect an insect or spider, or if collected we can release them after we take a few shots. Just as valuable, however, is the ability to view detailed, enlarged images on a computer screen while we pore over identification resources.
We are fortunate in our ability to employ a wide range of imaging systems. Our telephoto ‘bird lens’ works really well for large or skittish insects like butterflies, wasps and dragonflies. We use macro lenses for field photography of smaller, slow moving invertebrates. And we have dedicated photography lenses and equipment for specimens under the microscope, drawing on our professional experience as biologists in past lives.
Tip 2 – Take lots of photos, and from all angles
Sometimes it is the most unpromising looking photograph that provides the vital piece of information needed for identification. And once you become familiar with a group, you tend to know what features to try for. For example, with dragonflies I always try to get shots of the wing venation and also the colouring on the abdominal segments.
Microscopy
There are two main types of microscopes widely available for home use: ‘compound’ and ‘dissecting’ microscopes.
Compound microscopes are not very useful for invertebrate identification, unless you are interested in animals that are truly ‘micro’, and invisible to the naked eye. Compound microscopes are used to view VERY small structures, and such objects need to be mounted on a glass slide. Light is shone up through the object, so the material needs to be transparent. Many people will have used such microscopes at school or university to examine plant cells or perhaps their own cheek cells.
Dissecting microscopes, on the other hand, are extremely useful tools. They have a large working area and light may be shone from above, not through, the object. Therefore they can be used to examine intact specimens, including living animals and plants. (Note that in commercial product lists, dissecting scopes are sometimes called 'stereo-microscopes', although strictly speaking this term refers to the number of eyepieces not the type of scope).
Tip 3 – Invest in a dissecting microscope
Reasonable quality microscopes are actually quite affordable (e.g from $200-$300). If you plan to get serious about insect identification, or you are working on plant material, a dissecting microscope is invaluable. A bright desk lamp can be used as the light source, particularly if the lamp can be positioned to direct the light onto the microscope stage from a range of angles.
Raising larvae
Many insects have larval stages that have a completely different appearance to the adult. Butterflies, moths, beetles, and wasps, are examples of such ‘holometabolous’ insects. Collecting and raising larvae through to the adult stage is one way to help identify the species. Lepidopteran larvae (the ‘caterpillars’ of butterflies and moths) are particularly amenable to raising, so long as they are supplied with their specific host plant food.
During their development, many caterpillars change their appearance quite dramatically. For this reason, raising caterpillars through to the adult can sometimes be the only way to identify the species.
To read more, see our 14/9/17 blog post Studying lepidopteran life histories.
A cautionary note regarding collection
From many locations, including all national parks and nature reserves, collection of biological materials is not permitted. Always check the laws in your area before removing any plants or animals.
Key resources
iNaturalist – powerful, global and local
In recent years, the use of iNaturalist in Australia has grown rapidly. It has become our go-to resource for insect identification, whether we are looking to photo match or upload our sightings for assistance from specialists. And the computer vision (‘AI’) is extremely powerful too, particularly for some taxa such as moths, butterflies and dragonflies.
But the real power behind iNaturalist is the people involved. People with specialised interests and knowledge of all manner of organisms.
In addition, the platform is easy to use and you can search defined regions.
Tip 5 – use iNaturalist
Search for your species on iNaturalist, or simply add your sighting and let others – and the Computer Vision – assist. We’ve found that for many common species, the artificial intelligence system is extremely good. And even if it can’t find the species, it can provide hints to candidate family or genus level. That alone is a very helpful first step.
Tip 6 – Build or access a library of reference books
There is something about a book. We make extensive use of the internet (of course), but we still nearly always reach for a physical field guide if we have one, flicking through to look for clues. And we still consult seminal texts such as CSIRO's Insects of Australia for a more technical overview.
Tip 8 – Finally, be prepared to get it wrong - it's OK!
No matter how thorough you are with your research, it is always possible to get it wrong. That is simply the nature of the activity. Even the experts often have to revisit and revise their identifications.
Our own rule-of-thumb is this. If, on the weight of several lines of evidence, one candidate identification is most strongly supported, we are willing to call it. However, if there is nothing favouring one possibility over another, we stop at the taxon above. That is, if it could equally be species A or species B, we will simply call it at the genus level. Keep notes on how you reached your decision. When new evidence comes to light, you can then retrace your steps and reassess.
And this is how iNaturalist is designed.