I've had several people ask me in chat/private messages for advice as I've been keeping the same wahlbergii bloodline going since I got my L1 nymphs in August 2011, but I'm afraid that I may not be able to say that a few months from now. When my original stock became adults in December 2011, I mated all of the females without much difficulty. I joked that they bred like rabbits for me. All five of my females laid fertile ooths that produced over 600 nymphs. (It would have been more but I gave away a couple of the females after they laid a few ooths.) The majority of the other members who bought nymphs from the same seller back in August/Sept 2011 were not able to breed their wahlbergii. I'm not sure why. I was able to breed their offspring again without any issues. The females were quite obvious about spraying pheromones after dark, and I usually mated them late at night as soon as the female seemed receptive. The males usually connected shortly after mounting the female. I struggled a bit with the next generation but was again able to mate all of my females. I had to put the males on the backs instead of letting them mount on their own. Now their offspring are adults, and I've had difficulty mating all of my females this time (round # 4). The females don't seem as receptive to mating. The males mounted and tried to connect but were not able to. Many of the males were eaten. A few died of old age. Now I have a couple of females I got from another member (same bloodline/member got them from a friend who got them from me and bred them) who is not able to keep mantids in the summer. These females are receptive but the only fresh male I had showed no interest in mating and was finally eaten.
I've discussed this with one of the more experienced mantid breeders (his name is not listed above but this species is on his blog, and he started with this species in 2005), and he mentioned that he also had trouble keeping wahlbergii going for more than a few generations. I think hibicusmile has acquired different stock at times according to her bugatorium thread, but I'm curious how many generations she and Orin were able to keep going. I've heard others have had trouble keeping these going for more than 3 - 4 generations. The bad news is that others I have given/sold wahlbergii to this last time also had trouble getting them to mate...and a few of them are great breeders. That said, I think the stock SilentDevil got from a friend is the same bloodline as mine, and he's had some success as have a few others. So, there is hope...
Give them plenty of light and feed them a variety of insects. Heating them up seems to help but also sometimes seems to make them more aggressive. Try late at night instead of the daytime. I often have more success breeding in the summer/fall than I do in the winter/early spring. Unfortunately we've had such cold and rainy weather this spring that I haven't been able to catch many insects yet. I sometimes put my mantids outside in the sun, and it's been too cold to do that. Be careful if you do. Plastic enclosures in the hot sun will kill the mantis. I use net enclosures and put them outside the window by the computer so that I can watch them. Extreme temperature fluctuations can also kill them...even in net enclosures.
Good luck and let us know if you are able to breed them. Hoping some can keep these going.