Did the wife collect the beetle? When she did, she had the animals in her possession, the major pets in her household and the minor pets presumably in cages and this beetle and the other bugs in her inventory. Were any of them in his inventory? If not, maybe moving the bugs to his inventory would also achieve the wish for him? If some were in his inventory, that might not explain it, but I'm not sure what else might trigger the completion of one's wish and not the other. The goal is to have the animals, not necessarily adopt them.