J. Xantholophus are the largest of the 3 subspecies, followed by J. Jacksonii, and the smallest, J. Merumontanus (Mt Merus). Males typically have 3 horns, but the females can vary between the subspecies. Xanth females usually have no horns, or very tiny nubs, Jacksonii females have 3 horns and the Mt Meru females usually have a single rostral horn. Jacksons are so wonderful to keep - I have a 17 month old Xanth male and he is such a joy to own. Very laid back and very friendly!