10/24/2021: A new hobby Diploptera, revisited
Diploptera was sort of a buzz word a few years ago while some intense headlines about the future of “cockroach milk” were being circulated. For those who don’t want to mire through them, Diploptera are one of relatively few insects that possess true viviparity; eggs and developing nymphs are nourished directly by secretions within the females’ brooding invagination. This (it’s gross just having to type this, not because of the implications but because it’s a biological gray area in this context and it’s such a sensationalizing phrase) “roach milk” is extremely nutritious and the explanation for why Diploptera babies are larger, further developed, and with credit card bills and mortgages right out of the womb unlike other roaches with similar reproductive styles.
I’ve always found Diploptera to be quirky and active roaches; their chemical defenses permit them to be more bold than other roaches as there’s less risk to being active at any time when you can blast predators with secretions. There is some data suggesting they are photophilic in certain contexts as well. Unfortunately it wasn’t until recently that I learned their preferred enclosure conditions, which I had ignorantly offered and taken away from them multiple times over the years of culturing them. The best advice: hot and dry with something to drink. As a roach of oceanic islands they’re very well adapted to dry leaf litter and semi-arboreal habitats, including finding water in unconventional places. Their activities have even been classed as pesty when they decide to denude small trees of their bark to reach the moist cambium.
Previously it was believed that captive stock was Diploptera punctata. Unfortunately I no longer have stock from the original captive line (though that may change), however roachster supreme Alan Jeon was kind enough to facilitate sending some university stock my way.
The first thing I noticed about this new line was the… size. Diploptera punctata are not large roaches but the females are quite wide and bulky. The males, notably smaller, but not usually by too much except when compared to gravid females. This new line has veryyy tiny males, and the females are not as imposing as I recall. So today I decided to run this stock through a key provided by TJ, just to see if it turns up anything interesting!
In contrast to my optimism and skepticism… it would seem this is another line of punctata. The subsemicircular (apparently a word) pronotum, consistent dark brown color thereon and of the legs, and overall size (apparently other Diploptera species are ridiculously tiny relatively) suggest pretty strongly that this identification is correct. Oh well!
Supposedly… one of the original captive Diploptera lines somewhere is actually a different species, either parva or elliptica. Perhaps it will show its pronotum in the future long enough for me to acquire and key it out!
I’m not entirely disappointed with these results. There is some information suggesting Diploptera punctata populations are diverging rapidly, and there’s a substantial (but not enough to reproductively isolate) gap between populations at the base of their range and on the fringes where they’ve been introduced, such as Hawaii. Mixing two captive lines in an attempt to salvage my old colony actually proved impotent, and despite using healthy virgin adults of both sexes I was unable to get offspring despite proper husbandry. Admittedly, this is what spurred me to begin investigating the possibility of multiple Diploptera species lurking among captive lines.
Mysteries and discoveries regardless, it’s nice to have a hearty colony of Diploptera going again. Along with my Perisphaerus (more on those later) I had missed having the little roach-not-roaches around.
And to the adult male I had to sacrifice to get a good look at the features… thank you for your contributions to the progression of roach science!