Observations on the Cyclorrhaphan Larval Peripheral Nervous System: Muscle and Tracheal Receptor Organs and Independent Peripheral Type 11 Neurons Associated with the Lateral Segmental Nerves

Abstract

Muscle and tracheal receptor organs, connected to the lateral segmental nerves, are described; they are similar to the stretch receptor organs recorded in Orthoptera, Odonata, Hymenoptera, and Lepidoptera by previous workers. They contain at least one multipolar neuron and are invested in a connective tissue sheath continuous with the neural lamella of the adjoining lateral segmental nerve. Nerve connections pass to the segmental nerve, neighboring muscles, and in specific cases to a trachea when they may be involved in control of spiracular activity. Connections also sometimes occur between receptor organs of consecutive segments. The organs are located in thoracic and abdominal segments, three or more serially homologous pairs occurring in abodminal segments 1 to 7. Independent of the receptor organs, and contained within the terminal branches of the lateral nerves, are multipolar nerve cells, probably so-called Type 11, sensory neurons.