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A peculiar population of Leuctra larvae with horn-shaped lateral protrusions on the head, similar to Leuctra signifera and herein named Leuctra cf. signifera, has been collected in the Eastern Carpathians. This species, at the larval stage, lacks ommatidia and shows on the two horn-shaped lateral protrusions of the head cuticular structures represented by scales, three kinds of sensilla (numerous short thick bristles, some campaniform sensilla and few trichoid sensilla) and some coniform chloride cells. The short thick bristles belong to mechanoreceptors of the 'bristle type', the most common type of mechanoreceptor in insects usually responding to direct touch, while the campaniform sensilla are important receptors where mechanical deformation of the cuticle might occur. The trichoid sensilla show an insertion in the cuticle similar to that of 'filiform hairs', particular insect mechanoreceptors usually responding to movements of the surrounding medium. The lack of ommatidia in the larvae of L. cf. signifera and the presence of horn-shaped lateral protrusions rich of mechanoreceptors where eyes are usually located are features whose reason is so far not known. [ABSTRACT FROM AUTHOR]

The structure of the campaniform sensilla of the cricket eye was investigated by light and electron microscopy. Each sensillum is innervated by a single bipolar neuron. Its axon extends through the retina into a side-branch of the nervus tegumentarius. The dendrite extends through a cuticular channel to the surface of the cornea. The distal part of the dendrite, the sensory process, contains a tubular body and is attached to a cuticular cap which is obliquely inserted into the exocuticle between the corneal lenslets. Some particular structural features as well as the function of the campaniform sensillum of the cricket eye are discussed. [ABSTRACT FROM AUTHOR]