Ocellus of honey bee. After Snodgrass (1956, fig. 98g) Anatomy of the honey bee,
, Ithaca, p.334, (1956)
[1].

Abbreviations:
a - interstitial cells
Ct - cuticle
Epd - epidermis
Ir - iris cells
Ln - lens
Nv - nerve
Pg - pigment
Ret - retina
VB - vitreus body

The ocelli can be used by bees to detect light intensity during dawn and dusk Die Orientierung der Honigbiene in der Dämmerung, zugleich ein Beitrag zur Frage der Ocellenfunktion bei Bienen,
Z. vergl. Physiol.
, Volume 49, p.420-458, (1965)
[2].
See also Regional differences in the preferred e-vector orientation of honeybee ocellar photoreceptors,
Journal of Experimental Biology
, (2017)
[3]