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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 ...
[11] [21] The ocelli are not homologous to the simple eyes of caterpillars which are differently named as stemmata. [5] The ocelli of Lepidoptera are reduced externally in some families; where present, they are unfocussed, unlike stemmata of larvae which are fully focussed. The utility of ocelli is not understood at present. [5]
The ocelli are in an otd-rich area and disruption of otd results in loss of the ocelli, but does not affect the compound eyes. [10] Inversely, the transcription factor dachshund (dac) is required for the patterning of compound eyes, but mutants lacking dac do not exhibit loss of the ocelli. [11] Different opsins are used in the ocelli of ...
Some reptiles, such as the sand lizard of Europe, have eyespots; in the sand lizard's case, there is a row of spots along the back, and a row on each side. [12]Many species of cat, including Geoffroy's cats, jungle cats, pampas cats, and servals, have white markings, whether spots or bars, on the backs of their ears; it is possible that these signal "follow me" to the young of the species.
Neuropterans are soft-bodied insects with relatively few specialized features. They have large lateral compound eyes, and may or may not also have ocelli.Their mouthparts have strong mandibles suitable for chewing, and lack the various adaptations found in most other holometabolan insect groups.
The nervous system consists of two ventral nerve cords, which are usually fused into a single structure, and three or four pairs of smaller nerves per body segment. Only a few aquatic oligochaetes have eyes, and even then they are only simply ocelli. Nonetheless, their skin has several individual photoreceptors, allowing the worm to sense the ...
Ocelli are present; the fourth tarsal segment is cylinder-shaped. The four large wings are translucent, smoky grey, or mixed, and the anterior pair is slightly longer than the posterior one. Their aquatic larvae are used as fish bait and are called hellgrammites.
The ocelli, when present, are located in the top of the head, arranged at the corners of a triangle in an area called stemmaticum or ocellar triangle. For the purpose of systematics, the presence, the arrangement, and the conformation of the cephalic bristles is important and they have a specific terminology.