Morphology of the neuroendocrine systems of two larval blackflies, Prosimulium mixtum/fuscum and Simulium venustum

The anatomical relations of the neuroendocrine systems in larvae of Simulium venustum Say and the complex of Prosimulium mixtum Syme & Davies and P. fuscum Syme & Davies are described from histological examination. The neuroendocrine system in the brain showed morphological similarities to culicids (3 pairs of cerebral neurosecretory cell clusters and 1 pair of nervi corporis cardiaci entering the corpus cardiacum glandular system). The retrocerebral glandular portion of the neuroendocrine system was composed of a corpus allatum, corpora cardiaca and surrounding peritracheal gland. The morphology of the simuliid neuroendocrine system is discussed in relation to those of other families of Nematocera and higher Diptera..