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The term "ocellus" (plural ocelli) is derived from the Latin oculus (eye), and literally means "little eye". In insects, two distinct ocellus types exist: [9] dorsal (top-most) ocelli, and lateral ocelli (often referred to as ocelli and stemmata, respectively), most insects have dorsal ocelli while stemmata are found in the larvae of some ...
Ocelli (the plural of ocellus) are a type of simple eye, or eyespot. They are photoreceptive, but very simple; differing from complex eyes with compound lenses, ocelli cannot morph the sensation of light into a complete image, and are utilized to sense movement and the absence and presence of light.
Back of Macrobdella decora – note the row of orange dots down the middle and the two sets of black ones on the sides.. Macrobdella decora is a medium-sized leech, growing between 5 and 8.5 cm (2.0 and 3.3 in) long, and weighing from 1.48 to 3.69 grams (0.052 to 0.130 oz).
The scape and pedicel generally comprise a single segment each. The antennal formula is used to describe the number of segments in each of the components of the antenna (scape; pedicel; anelli, funicle; clava). An antennal formula of 1:1:2:4:3 indicates an antenna with a scape, a pedicel, 2 anelli, 4 funicular segments, and 3 segments in the ...
The principal and secondary eyes likely evolved separately, with the principal eyes being homologous to the ocelli of insects but the secondary eyes being derived from compound eyes. Since the secondary eyes lack the remnants of the borders between the ommatidia typically present in eyes evolved through fusion of the ommatidia, it is more ...
In almost all genera is a pair of ocelli near the base of the head, and in a few, the elytra cover the entire abdomen. The maxillary mala of larvae are strap-shaped, but not as long as in the Proteininae , and the mandible lacks a prostheca .
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The lateral ocelli evolved from compound eyes and may have a tapetum, which enhances the ability to collect light. With the exception of scorpions, which can have up to five pairs of lateral ocelli, there are never more than three pairs present. The median ocelli develop from a transverse fold of the ectoderm.