He studied Secondary Education in Vigo and Natural Science and Medicine in Madrid. In 1918, he took his doctor's degree in Natural Science with the thesis Curculiónidos de la Península Ibérica e Islas Baleares. In 1919, he got his degree in Medicine at Santiago University. Luis Iglesias devoted himself to teaching and enthomological research. He became dean at the Faculty of Science, rector at University and president of the Seminary of Galician Studies. In 1947, he became a member of the Galician Academy and made his speech Las especies del género Carabus en Galicia.
Some of his most important works are: Algunas especies nuevas o poco conocidas para la fama ornitológica de Galicia, Reconocimiento de tejidos vegetales por reactivos microquímicos, Los prados de las regiones media y montaña de Galicia, Descripción de tres yacimientos gallegos de evansita, La lucha antiacrídica, Fauna de Galicia I. Cerambícidos de Galicia II. Especies del género "Carabus" en Galicia, Variabilidad por fluctuación de las manchas elitrales de "Crioceris asparagi", Biología de los parásitos del hombre...Luis Iglesias also collaborated in the work Historia de Galiza, by Otero Pedrayo, writing the Zoology section.