I need a protocol for determining the age of beetles based on their morphological structures such as wings, labro, etc. Is it possible? I know that the age of bees may be stimated by wing wear, since wings are not repaired as the animal ages.
Dear Francinaldo,
Perhaps a more experienced coleopterist can give you a better answer, but I'll see if my personal experience can give you some pointers. The quick answer is that this is going to vary according to species, so you will need to compare beetles of known ages. I've been fortunate enough to work on two groups, the Passalidae and Paropsini (Chrysomelidae), that change colour as they age. Passalids turn from light brown to completely black, so can be ranked according to colour. These beetles live in family groups, so you can often pick out the parental pair of beetles as the blackest ones. Paropsini undergo a more striking change of pattern, which was very useful for separating the parental and filial generations of adults in the field.
If colour (and the obvious measure of cuticle hardness in the first weeks) does not work, then you can examine parts of the beetle that they use in their daily activities. Their shiny cuticle gets scratched, and if they do things like dig, parts of the body like the fore-tibia wear down. Setae break off, too. Again, in a family of passalids, you can pick out the parental pair from wear and tear alone.
There are more clues to age by looking internally, but I gather you're not dissecting them.
Kind regards, Owen.
Thanks Owen. The animals of my interest are small beetles of the genus Paederus (Staphylinidae). I will examine the coloration according to the age. Good answer.
Dear Francinaldo,
The degree of wornedness (the size) of the mandibles may help to assess the age of a beetle as well as the cuticle parts regularly contacting soil as Owen put it.
Dear Francinaldo,
if you are working with Paedurs, you should definitely ask Joachim Willers at Museum für Naturkunde Berlin:
http://www.naturkundemuseum-berlin.de/institution/mitarbeiter/willers-joachim/
He is a well-known specialist for this genus and probably knows best about coloration of Paederus specimens.
Best regards
Armin
Dear Francinaldo,
The degree of sharpness of the jaw is in general is a good indication of the age of the specimens for species that have chewing mouthparts. For example, specimens of wintering Capnodis (Buprestidae) have mandibles rounded compared to newly emerged. For the color, if species have dark colors, everything becomes even more complex because you also have shade variations with respect to moisture. Missing or broken parts of the legs unfortunately doesn't indicate the age even though they give some indications on the activities of the specimen. It would be appropriate to estimate the age cohorts of specimens coloring the elytra from individuals with known age and then observe changes in estimate.
Best Regards
Carmelo
Thanks Bonsignore. Paederus beetles are predators on a variety of insects. I also think that the mouthparts may be worn out as beetles age and it may constitute a good trait for assessing the age. I will check it out. Ta!
Burrowing beetles that have tibia 'teeth' with which they dig show greater wear of the teeth the older they are.
Mandibular wear has been used very generally to determine new versus older individuals in tiger beetles. In a paper in Cicindela 29:23-29, (Patterns of mandibular wear in Cicindela sexguttata) Kritsky and Simon did a more detailed study of aging in a species of tiger beetle, using mandible wear and tooth breakage to provide an indication of age.
Dear Francinaldo,
For the genus Paederus as mostly active predators , i think that the size of mandibules , main active mouthpart , can give you an idea about the age: the more they are used the more the insect is old. You can use morphometrics and set your own scale corresponding the age with the size of the mandibules. you can also use the possible variations of the body color as younger insects have brighter colors while the older ones are generally darker
OK, Barry and Chermiti, Thanks. Very interesting. I will check it out.
Hi Francinaldo Silva,
I think your finding should be vary, basically based on the size of the observed beetle. Usually larger beetle has longer life span. Same goes to the predicting the age. All I know, newly emerge beetle or newly passed molting, the body would have lighter coloration. Best solution is that try to keep the beetle in lab and observe it.
Best wishes.
OK, Abdulah. I am making a big effort to keep the insects alive for further lab tests. Thanks.
Dear Francinaldo Silva, A long time has passed and I hope you found your answer for determining the age of adult beetles based on their morphological aspects. Colin J. Hawes touched on tibial wear. This has become a standard method in Australia, first developed by Dr. Marina Tyndale-Biscoe. See her PhD thesis from James Cook University. And:
Tyndale-Biscoe, M. (1978) Physiological age-grading in females of the dung beetle Euoniticellus intermedius (Reiche) (Coleoptera: Scarabaeidae). Bulletin of Entomological Research, 68, 207–217.
Not sure if you still need this answering but here's a paper
Mechanical properties of the beetle elytron, a biological composite material
by Lomakin, Joseph; Huber, Patricia A; Eichler, Christian; More...Biomacromolecules, 02/2011, Volume 12, Issue 2
I am currently developing a method to determine the age of the Tansy beetle.
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