I did an experiment with cockroaches

[bugmankeith]

I took and empty tank put some wood chips and decor in it and placed a male dubia roach, and a female fusca roach. Right away the male tried to mate with the fusca (without any luck). This went on for a few days without any change. Eventually, the dubia stopped trying to mate with the fusca, but always followed her around.

I left ONLY those 2 roaches in a tank for an entire year, they both are alive. So I thought to myself, "what if I placed a virgin dubia female in the tank, will the male mate with her?".

I placed a virgin female dubia in the tank, not only did the male not even try to mate with her, he completely ignored her presence, and continued to stay by the fusca female, even though she is completely different in size and looks of a female dubia! It's almost like he thinks that is the female of his species, or he gave up on mating after being "rejected" so many times.

I was sure he would mate right away with the dubia female, but I was wrong. Very interesting!

 

[ZephAmp]

Are the two still together? Have you been observing the 24/7? Was the female dubia isolated since she was a subadult or was she just any random adult female from your colony?

Roaches can get the deed done very fast. I've seen discoids hooked up for less than a minute, only to isolate the female and find out she was preggo. You might see male mating displays but to catch them in the act you normally have to check your colony after dark. I'd bet if he's still physically capable of doing it, he'll mate with her ASAP. :}

 

[bugmankeith]

Are the two still together? Have you been observing the 24/7? Was the female dubia isolated since she was a subadult or was she just any random adult female from your colony?

Roaches can get the deed done very fast. I've seen discoids hooked up for less than a minute, only to isolate the female and find out she was preggo. You might see male mating displays but to catch them in the act you normally have to check your colony after dark. I'd bet if he's still physically capable of doing it, he'll mate with her ASAP. :}

The female was isolated as a subadult and she molted alone in a tank. Then I put her in with the male about 2 days after she molted. He was next to her and just slowly walked away.

I watched them for the first 2 days as the female was resting on a log and the male was still under his same hiding spot at the other side of the tank (its a 20 gallon long so big tank)

When the male was first put in the tank (with the fusca) he instantly raised his wings and followed her like crazy all day, he should have done that with the virgin female dubia, not one wing rais eor any mating behavior, he literally walked to the fusca, and dug under her and showed no mating behavior with the dubia.

 

[ZephAmp]

Depending on a myriad of other factors, the female dubia probably didn't secret attractive hormones. Interspecific mating interactions have been piecingly but extensively studied, but Blaptica x Blaberus relations are not recorded.
Here's a good paper with some neat stuff in it:
http://nsrdec.natick.army.mil/LIBRARY/70-79/R70-102.pdf

Based on their findings of Byrsotria sp. responding to Blaberus pheromones I would have to give a slight nod to the possibility of Blaptica responding as well. However, in your case, there is no interspecific mating or courting going on, so I would assume the sole reason the male dubia is sticking around the fusca is because she is producing comparably large amounts of attractant hormones (which to the extent of my knowledge are similar for most species of roach). These simply tell other roaches that there are other roaches in the area and to "join the party." Seeing as the fusca is bigger than the female dubia, it's a false cue to the male that there are more roaches over there than there are over by the female dubia.

 

[bugmankeith]

Wow that's amazing! It seems like that very well could be the reason for the confusion. Roach perfume, gotta love it! I call them the "odd couple".

 

[ZephAmp]

It also looks like she makes a good hiding place.

Where did you get your fuscas from, btw?

 

[bugmankeith]

It also looks like she makes a good hiding place.

Where did you get your fuscas from, btw?

yeah lol.

Blaberus.com is the Fusca she was actually mixed in with B. Giganteus, she outlived them all, got her 3 years ago, she's an old roach, didnt know they live that long. The Dubia are from a reptile expo here, but i'm sure you can find plenty online.