Studies on the genus Melipona 1 - Introduction and acknowledgements. 2 - Systematica. Three modern trends in the systematics of the Meliponini are cited: Ducke (1916), Schwarz (1932) and Moure (1946); The 14 species known of the genus Meliponaare given. 3 - Contribution to the Biology. There are three castes in Melipona: drones, workers and queens, which are easily distinguished on account of the differences in size, color, proportions and behavior. While the queen of Apis emerges in a state of sufficient development to be fertilized and to begin the laying of eggs, the queen of Melipona, on the other side, in a glance seems undernourished, get having received the same food as the workers, both in quantity and in quality. They emerge with undeveloped ovaries and, only after the fertilized queen is dead or too old, virgin queens may be fertilized and begin to be fed by workers. After 15 to 30 days, according to the number of workers and the food gathered, the queen begins to lay eggs. The queens, drones and workers emerge from cells of the same size and with more or less the same quantity of food. Variations of the quantity of food do not change the caste, but only the size of the bee. The caste determination in Trigonai (another genus of Meliponini) depends evidently upon differences in nutrition. It is easily seen that the cells which furnish drones and workers are different in size, though equal in form, from those from which emerge the queens. Somie data concerning the biology of the Meliponini are given below: 1st - The number of eggs laid by a queen: Melipona quadrifasciata anthiodioides - in 44 days (July 9th to Aug. 22nd - 1946) 590 eggs, with an average of 13 eggs per day, and a maximum of 22 eggs per day. Trígona (Plebéia) mosquito, (Mirim-guassú) - from July 9th to July 24th 1946, 249 eggs. Prom Aug. 9th to Aug. 24th, 1946 laid 1035 eggs; with an average of 69 eggs per day and a maximum of 120 eggs. 2nd) - A table is given showing the percentage of drones observed in the total of individuals in samples of brood combs. (See Quadro I and Quadro EE). 3rd) - The duration of the several phases in the lives of the Meliponaworkers and queens is: Phases Worker Queen Hatching of the egg 4,5 to 6,5 days 4,5 to 6,5 days Larva 7 to 8 days 7 to 8 days Prepupa 5 to 5,5 days 4,5 to 5 days Pupa 15,5 to 18 days 11,5 to 15 days Total, from egg to imago 34 to 37 days 30 to 34 days It is mentioned that the Meliponini constructs large honey and pollen pots of characteristic size, and form both In natural hives and in experimental colonies in wooden boxes. The workers in weak colonies of M. Marginata and M. schencki produce little wax, and excepcionally, use brood cells for storage Instead of pots, showing that their reactions are very variable. Other details of the brood cell, such as brood cells disposition, construction, destruction, etc., are discussed. 4 - Anatomy of the reprodutive organs. The sexual organs of the male consist of: a) Two testicles envolved by a thin membrane, each of the testicles formed by four testicular tubes, b) two vasa deferentia, c) two vesiculae seminales, which are spherical and very small, d) one ejaculatory duct and e) the pente. There are no accessory glands as in Apis and Bombus. (BORDAS, 1895) See Fig. 6 and 46). The reprodutive organs of the female consist of: a) two ovaries, each formed by four ovardoles. The length of these pvarioles is: 1,7 to 2,0 mms. in the worker or sterile female, 11,1 to 11,5 mms. in the virgin queen and 76 mms. in the fecundated queen (measures taken on Meliponafasciata melano ven ter), b) two oviducts, c) vagina and d) spermatheca with a pair of glands. This same description is applied to Trígona and Bombus, varying the proportions. 5 - Citology Studies on the cytology of the genera Melipona and Trigona were carried out Ovaries òf the pupas queens and workers, testicles of prepupas and young pupas of drones, brains and other somatic' ttisues of larvae were examined. The details of the technique and the results are given. ;The somatic tissue of the females, both queens and workers, presents 18 chromosomes. The spermatogeneáfó is normal, following the type described for Apis by Meves (1907) with expulsion of a cytoplasmatic Bud in the first division, and a nucleated bud in the second, The sperfiuatogonia and spermatids show 9 chromosomes. 'Polyploid c cel|sl and tissues are fre'quent, even in the testicles but polyploid secondary spermatocytes do not go through a second meiotic division. No polyploid individuals have been found às yet. The number of chromosomes is the same in all Melipona, studied: M. fasciata, M. marginata, M scheneki. M. quadrifasciata, A. e. 18 in the female and 19 in the male. 6 - Determination cf castes of queen and worker. There are many papers discussing the problem of caste determination in the social insects (Bibliography in the papers of Light, 1943 and Wheeler, 1928)* Two,, theoriescome always under discussion: a) the. Blasjtógezüc or; genptypJc determination and b) the Trophogenfè or somatogenic one. In the first case, special genes are supposed to be responsible while in the second case the determination is by means of food or other environmental factors. No one doubts today that the caste of .males In Hyme-hoptera is genetically determined by arrhenotoky, wjth very few exceptional casss. The Meliponabees do not escape this rule, as shown by chromosome counts. The opinions aré however divided with regard to the female castes.