The long and short of sperm polymorphisms in insects JOHN G. SWALLOW GERALD S. WILKINSON First published: 15 March 2007 https://doi.org/10.1017/S1464793101005851 Citations: 94 PDF TOOLS SHARE ABSTRACT Production of more than one morphological type of sperm in a common testis has been documented for a variety of invertebrates, including gastropods, spiders, centipedes, and insects. This unusual phenomenon is diffcult to explain by current theory, particularly since available evidence indicates that one sperm type is often incapable of effecting fertilization. In this review we critically examine evidence on the distribution and development of sperm heteromorphisms among insects in light of competing hypotheses for the evolutionary origin, maintenance, and function of a non‐fertilizing class of sperm. To date, no single hypothesis, including alternatives which assume non‐fertilizing sperm are non‐adaptive, or that they provision, facilitate, or compete wi...