Attygalle, A. B.; Billen, J. P. J.; Jackson, B. D.; Morgan, E. D. 1990. Morphology and chemical contents of Dufour glands of Pseudomyrmex ants (Hymenoptera: Formicidae). Zeitschrift für Naturforschung. C, Journal of Biosciences 45:691-697.

Schoeters, E.; Billen, J. P. J. 1990. Morphology of the venom gland in relation to worker size in leaf-cutting ants (Formicidae, Attini). Actes des Colloques Insectes Sociaux 6:249-252.

Billen, J. P. J. 1990a. Phylogenetic aspects of exocrine gland development in the Formicidae. Pp. 317-318 in: Veeresh, G. K.; Mallik, B.; Viraktamath, C. A. (eds.) 1990. Social insects and the environment. Proceedings of the 11th International Congress of IUSSI, 1990. New Delhi: Oxford & IBH Publishing Co., xxxi + 765 pp.

Billen, J. P. J. 1990b. Morphology and ultrastructure of the Dufour's and venom gland in the ant Myrmecia gulosa (Fabr.) (Hymenoptera: Formicidae). Australian Journal of Zoology 38:305-315.

Billen, J. P. J. 1990c. The sting bulb gland in Myrmecia and Nothomyrmecia (Hymenoptera: Formicidae): a new exocrine gland in ants. International Journal of Insect Morphology and Embryology 19:133-139.

Billen, J. P. J. 1990d. A survey of the glandular systems of fire ants. Pp. 85-94 in: Vander Meer, R. K.; Jaffe, K.; Cedeno, A. (eds.) 1990. Applied myrmecology: a world perspective. Boulder: Westview Press, xv + 741 pp.

Bagnères, A.-G.; Billen, J. P. J.; Morgan, E. D. 1991. Volatile secretion of Dufour gland of workers of an army ant, Dorylus (Anomma) molestus. Journal of Chemical Ecology 17:1633-1639.

Billen, J. P. J. 1991. Ultrastructural organization of the exocrine glands in ants. Ethology Ecology and Evolution Special Issue 1:67-73.

Billen, J. P. J.; Peeters, C. 1991. Fine structure of the gemma gland in the ant Diacamma australe (Hymenoptera, Formicidae). Belgian Journal of Zoology 121:203-210.

Peeters, C.; Billen, J. P. J. 1991. A novel exocrine gland inside the thoracic appendages ('gemmae') of the queenless ant Diacamma australe. Experientia (Basel) 47:229-231.

Schoeters, E.; Billen, J. P. J. 1991. Morphologie des glandes pro- et postpharyngiennes chez Atta sexdens (Hymenoptera: Formicidae). Actes des Colloques Insectes Sociaux 7:153-160.

Billen, J. P. J. (ed.) 1992. Biology and evolution of social insects. Leuven: Leuven University Press, ix + 390 pp.

Billen, J. P. J. 1992. Origin of the trail pheromone in Ecitoninae: a behavioural and morphological examination. Pp. 203-209 in: Billen, J. P. J. (ed.) 1992. Biology and evolution of social insects. Leuven: Leuven University Press, ix + 390 pp.

Peeters, C.; Billen, J. P. J.; Hölldobler, B. 1992. Alternative dominance mechanisms regulating monogyny in the queenless ant genus Diacamma. Naturwissenschaften 79:572-573.

Schoeters, E.; Billen, J. P. J. 1992. Morphological and ultrastructural study of the metapleural gland in Diacamma (Hymenoptera, Formicidae). Pp. 239-247 in: Billen, J. P. J. (ed.) 1992. Biology and evolution of social insects. Leuven: Leuven University Press, ix + 390 pp.

Billen, J. P. J. 1993. Morphology of the exocrine system in ants. Materialy Kollokviumov Sektsii Obshchestvennykh Nasekomykh Vsesoyuznogo Entomologicheskogo Obshchestva 2:1-15.

Billen, J. P. J.; Taylor, R. W. 1993. Notes on the aberant venom gland morphology of some Australian dolichoderine and myrmicine ants (Hymenoptera, Formicidae). Belgian Journal of Zoology 123:159-163.

Keegans, S. J.; Billen, J. P. J.; Morgan, E. D.; Gökcen, O. A. 1993. Volatile glandular secretions of three species of New World army ants, Eciton burchelli, Labidus coecus and Labidus praedator. Journal of Chemical Ecology 19:2705-2719.

Nascimento, R. R. do; Billen, J. P. J.; Morgan, E. D. 1993. The exocrine secretions of the jumping ant Harpegnathos saltator. Comparative Biochemistry and Physiology. B. Comparative Biochemistry 104:505-508. PDF

Schoeters, E.; Billen, J. P. J. 1993a. Anatomy and fine structure of the metapleural gland in Atta (Hymenoptera, Formicidae). Belgian Journal of Zoology 123:67-75.

Schoeters, E.; Billen, J. P. J. 1993b. Glandes coxales de Pachycondyla obscuricornis (Formicidae, Ponerinae). Actes des Colloques Insectes Sociaux 8:183-186.

Billen, J. P. J.; Schoeters, E. 1994. Morphology and ultrastructure of the mandibular gland in Formica L. ants (Hymenoptera, Formicidae). Memorabilia Zoologica 48:9-16.

Oldham, N. J.; Morgan, E. D.; Gobin, B.; Billen, J. P. J. 1994. First identification of a trail pheromone of an army ant (Aenictus species). Experientia (Basel) 50:763-765. PDF

Oldham, N. J.; Morgan, E. D.; Gobin, B.; Schoeters, E.; Billen, J. P. J. 1994. Volatile secretions of Old World army ant Aenictus rotundatus and chemotaxonomic implications of army ant Dufour gland chemistry. Journal of Chemical Ecology 20:3297-3305.

Schoeters, E.; Billen, J. P. J. 1994. Nouvelles données structurales sur la glande à venin chez Atta sexdens rubropilosa et Myrmica sabuleti (Hymenoptera, Formicidae). Actes des Colloques Insectes Sociaux 9:67-73.

Gobin, B.; Billen, J. P. J. 1994. Spécificité de la phéromone de piste chez Crematogaster scutellaris et Crematogaster laestrygon. Actes des Colloques Insectes Sociaux 9:35-39.

Billen, J. P. J. 1994a. Morphology and classification of the exocrine glands in ants. Ari 18:1-4.

Schoeters, E.; Billen, J. P. J. 1994a. The intramandibular gland, a novel exocrine structure in ants (Insecta, Hymenoptera). Zoomorphology (Berlin) 114:125-131.

Billen, J. P. J. 1994b. Morphology of exocrine glands in social insects: an up-date 100 years after Ch. Janet. P. 214 in: Lenoir, A.; Arnold, G.; Lepage, M. (eds.) 1994. Les insectes sociaux. 12ème congrès de l'Union Internationale pour l'Étude des Insectes Sociaux. Paris, Sorbonne, 21-27 août 1994. Paris: Université Paris Nord, xxiv + 583 pp.

Schoeters, E.; Billen, J. P. J. 1994b. The venom gland in formicine ants: an ontogenetic and ultrastructural study. P. 218 in: Lenoir, A.; Arnold, G.; Lepage, M. (eds.) 1994. Les insectes sociaux. 12ème congrès de l'Union Internationale pour l'Étude des Insectes Sociaux. Paris, Sorbonne, 21-27 août 1994. Paris: Université Paris Nord, xxiv + 583 pp.