of the genus Azteca which inhabit the hollow stems of these fast growing trees. Stingless bees. One of his favourite topics was the life habits of the stingless honey-bees Melipona and Trigona. They are protected by a venom which they squirt when disturbed. The local name for them is Cagafogo (fire-shitter). Dimorphism in midges. Another discovery was the dimorphism in midges of the family Blephariceridae. There are two female forms with different mouth-parts: one sucks blood, the other takes nectar, as does the male. To prove the point to skeptics, he sexed the flies carefully, and reared them from pupae. Termites. By studying living termites Müller was able to correct many errors to be found in textbooks. For example, their caste system is organised quite differently from ants, since the castes contain members of both sexes, whereas in Hymenoptera the castes are unisexual and the males are haploid. Termites are placed in a completely distinct order from ants, traditionally the Isoptera. Botanical work. Much of Müller's botany was stimulated by the series of botanical works published by Darwin in the years after the Origin. Müller made contributions in all these fields. After Darwin's Fertilisation of Orchids (1862) he spent years of work on orchids, sending observations to his brother Hermann and to Darwin. Darwin used some of this work in his second edition of 1877, and Hermann later became famous for his work on pollination. On Climbing plants (1867) Müller lent a letter to Darwin listing 40 genera of climbing plants classified by their method of climbing. The next few months saw more observations, which Darwin had translated and published as Müller's first paper in English. As a botanist, Fritz Müller is denoted by the author abbreviation F.J.Müll. when citing a botanical name. Müller and Darwin Müller became a strong supporter of Charles Darwin. He wrote Für Darwin in 1864, arguing that Darwin's theory of evolution by natural selection was correct, and that Brazilian crustaceans and their larvae could be affected by adaptations at any growth stage. Müller sent a copy to Darwin, who had the book privately translated for his own use. A later translation into English, with some additional material by Müller, was made by W.S. Dallas, and was published as Facts and Arguments for Darwin in 1869 (Darwin sponsored the translation and publication). Extensive correspondence exists between Müller and Darwin, and Müller also corresponded with his brother