Can Stick Insects really mate for 1400 hours?
I saw this tweet a while back, and it made me awfully curious:
Is that true? Because that seems like not a very smart thing to do, if you are a large and tasty insect. Or, in this case, two large leaf-eating insects belonging to a group that specializes in being invisible to predators by looking like a stick.
Two sticks having sex is the sort of thing I’d notice, anyway.
The risk of predation while you are hooking up is a major issue. You can see from this photo that a fair amount of Kama Sutra-ish contortion is needed to successfully maneuver into place. This does tend to inhibit one’s ability to run away!
Several different sources repeated that stick insects remain paired for up to 79 days, but I was not able to find an original reference giving the details. Some of the references cited date back to 1910, so not surprising that I can’t get my hands on a digital copy.
From one paper describing mating behavior:
“The Indian stick insect Necroscia sparaxes may remain coupled for up to 79 days (a record for insects)…Intromission may occur only initially or intermittently. In either case, a substantial proportion of male time-investment is not spent in ejaculate transfer.
In captivity, Diapheromera veliei and D. covilleae pair for 3 to 136 hours and the penis may be inserted and removed up to 9 times. The genitalia are not in contact for ca. 40% of this period, and attachment is maintained by a male clasping organ.
I did find a clear, verifiable report of coupling for 136 hours (5¾ days), but what is important here is that the insects were NOT having sex (intromission, or penis in vag) the entire time.
It’s generally thought that the male hangs around in order to have repeated matings, but also to drive off other males. I found several reports of stick insect menage a trois (or sept) in the literature, including this etching of kinky stick insect activity. The male is–literally–cock-blocking a competitor.
So, it’s probably correct to say that stick insects can remain paired for up to 79 days, even though we can’t verify that directly. It is less correct to say that they “have sex” for 79 days, just as it would not be technically correct to say you mated for 8 hours if you had sex at 10pm and again at 6am. Well, unless you are into that tantric stuff, anyway.
And since 1400 hours = 58 days, the numbers don’t match up, and it is not correct that they mate for 1400 hours. It’s more like 1,896 hours.
Sivinski, J. (1978). Intrasexual Aggression in the Stick Insects Diapheromera Veliei and D. Covilleae and Sexual Dimorphism in the Phasmatodea, Psyche: A Journal of Entomology, 85 (4) 405. DOI: 10.1155/1978/35784