1. Alten, H. Von. (1910) Zur Phylogenie des Hymenopteran gehirns Jena. Z. Naturw., 46, pp. 511 - 590.
2. Berlese, R. (1907) Gli insetti, 1.
3. Buxton, P.A. (1917) On the protocerebrum of Micropteryx (Lepidoptera) Trans. R. ent. Soc. Lond., 1, pp. 112 - 153.
4. Dogra, G.S. and Tandon, B.K. (1964) Adaptation of certain histological techniques for in situ demonstration of the neuroendocrine system of insects and other animals Q. J. microsc. Sci., 105, pp. 453 - 466.
5. Dujardin, F. (1850) Memoire sur le système nerveux des insectes Ann. Scot. nat. Hist., 3(14), pp. 195 - 205.