Rhonda Bracey: At Random

Well, you learn something new everyday! Today I learned a lot.

I learned how to tell male and female native cockroaches apart (it’s called ‘sexing cockroaches’). I learned that ‘my’ native cockroach might be a new species or possibly an undocumented geographic variation. I also learned that diurnal cockroaches (those that hang out in the daylight hours, like ‘my’ native cockroach) are pretty rare and that scientists are researching their properties for sunblock applications, amongst other things!

So how did I learn all this? Martyn, from the Australian Museum in Sydney, replied to my email giving me a whole lot of info about this cockroach and why he wants me to send him any more that I might find. Here are some excerpts from his email:

I have an interest in the diurnal native cockroaches. Australia is very unusual in having a number of species which are not only active by day but are fond of basking in the sunlight. Overseas cockroaches (and many other Australian species) die if exposed to UV light for any length of time. Some of our native species are creating interest as they seem to produce a natural ‘sunblock’ which may have a commercial application…(Actually the sunblock cockroaches are in a different genus Anemesia – so they’re about as closely related to yours as dogs are to foxes – still there are other compounds of use found every day in the natural world – e.g. leech spit is used in bruise ointments. Who knows what could be in your cockroach?)

The genus Polyzosteria is one where all members of that genus are diurnal and often colourful. There are only about a dozen known species. Yours seem to be a member of that same genus but I cannot be sure of the species although it is very similar to Polyzosteria cuprea…

This means it is either a new species to science, or a geographical variation of a known species (P. cuprea), or it is one where the colours change after death so the live ones look superficially different to the dead ones until you get down to comparing the numbers of leg spines, genitalia, size etc. At this stage it is a bit of a mystery.

Should you find any more we would be interested in some specimens. If dead, please remember to include any legs etc. which drop off as they are important too – as is a slip of paper with all the details of its finding like where, when, and your name and contact details. In this way if it proves to be something new they can get back in contact with you and include this information on the record for the species (whether it is a known one or not, your details will be linked to that specimen as the collector for as long as the specimen exists – maybe a century or more).

If it is alive the system is pretty much the same except that the specimen/specimens will need to be packed in a slightly larger plastic container with some small ventilation holes and a few pieces of bark or dead leaves included so the contents won’t slide or rattle around during transit. Express Post is preferred in this case.

Once again all details of the collection should be included as the specimen, once it dies, will be included in the entomology reference collection pending what it turns out to be. For the record your photo shows a female as you can see the last body segment on the tail end has a cleft in it making it look a bit like the letter ‘m’. In the males this cleft is missing. Below is a photo of a female of the Polyzosteria species local to the Sydney region. Notice the cleft on the last abdominal segment matches the shape of the one in your photo: http://davidavid.blogspot.com/2006/04/diurnal-cockroach-polyzosteria-limbata.html and the male ’end’ looks like this – ignore the fact that it is another species – just look at the shape of the end edge of the last abdominal segment: http://agspsrv34.agric.wa.gov.au/Ento/images/P_mitchelli.jpg.

So there you have it! ‘My’ cockroach could be a new species and my details as a collector could be kept for 100 years or more!! Who’d have thought a pretty cockroach on a wall could be so interesting?

Oh, and here’s the picture that started all this:

Female native cockroach on house wall