Lighting for Invertebrates
I keep a group of giant prickly stick insects in a large glass vivarium and have spoken to a friend who recommends UV lighting for them, but why and how would it be of use to them?
The thinking and science behind lighting exposure for many species of animal is moving ahead at a very rapid rate. Scientific research is revealing more and more information about reptiles, amphibians and invertebrates and their relationship with the sun. It is true to say that we are far more knowledgeable about reptiles and amphibians than ever before, while at present, research into the impact of lighting for invertebrates is very much in its infancy.
But the sun is the world’s best source of free energy. It provides light and heat, and the wavelengths of light that are known as ultraviolet (UV). It would seem most unlikely to me that invertebrates would not have evolved to make use of such energy in some way.
Increasing levels of research
Q. Jamie, you certainly have a fantastic collection! Can you please give me some insight into how you plan your breeding programme?
There are many people around the world working with and investigating the effects of differing light levels and UV indexes on this group of creatures. There are also dedicated zoo groups that are starting to concentrate on this very subject, by investing time and money in research too. In addition, private keepers are now already including UV lamps with certain species of spider and scorpion.
I have also had quite a few emails from phasmid keepers who are trying our systems above both stick insects and leaf insects. The majority of phasmids live off the ground in trees and bushes, and so are exposed to sunlight under normal conditions.
For all other invertebrate species, consider their lifestyles carefully. Most significantly, if it seems that the creature is exposed to natural light in the wild, then this is a good indicator that it could also benefit from artificial lighting of this type as well.
Clearly, your friend has found that some exposure can be beneficial. There is on-going scientific research being carried out in laboratories, and advancing product lines is driving research on behalf of the brands. But for me, the best source of research indicators always comes from keepers of such creatures, who are working with them at home.
These are the people that keep one or more species and care for them on a daily basis in a dedicated way. Their observations can be recorded and shared, and once they start to become commonplace in the hobby, this then spurs the scientific community to investigate the matter further.
As things stand, there is no definitive answer to your question as yet, but based on existing knowledge, it is possible to draw a few conclusions. We know for instance that insects appear to use the UVA component in sunlight rather like birds, amphibians and reptiles. Access to UVA seems to “activate” the insect’s compound eye and allows them to find food and even mates.
It does seem that certain flowers and pollens display fluorescent markers that are only visible to these types of eye and if illuminated under adequate UVA. There is plenty of research already available on bees and you can read more about this subject online. It also seems that this type of vision can play a part in mate selection and the recognition of hive members, in the case of these social insects.
It is also common to see tarantulas stand up on their back legs under a lamp and sway back and forth, exposing their underbelly to the light. They only seem to do this for blocks of a few minutes at a time. The truth is, however, that we do not currently understand the reasons why they act in this way, but such behaviour is observed quite regularly. This for me is an indicator that UV is important to these arachnids, and it is another aspect that now needs proper scientific investigation.
Initial results are positive
In the case of giant prickly stick insects, there are a number of keepers in the UK already using UV systems over these particular phasmids. Furthermore, the initial results do indicate that these insects seek out and use this UV source. The common observations from all sources are that they display vastly better/brighter colouration, and have about a 10-15% increase in terms of their reproductive lifespan and their overall life expectancy in the case of females, when compared with others kept in similar conditions without illumination.
So presently, the answer to your question would have to be that it is early days still, and much research must be completed to prove the case, but initial results suggest there are some benefits to using UV lighting with these insects. We also know that the adequate provision of UVA helps with insect vision, and insect behaviour can be changed when these systems are provided.
I would therefore suggest that if you want to try it, please do so and feel free to contact me with your findings. It must be emphasised that as with all species, the light and shade method should be employed. The proper provision of UV lighting requires that areas of light and shade are provided and that the animal is allowed to self regulate its own exposure as it wishes, moving from one area to another. The need for graduated shade in their quarters cannot be overemphasised when you are using high intensity lighting.
© John Courteney-Smith
Taken from “Practical Reptile Keeping” magazine