The Structure and Function of the Insect Dorsal Ocellus

An ocellar "pupil" that does not change with light intensity, but with the insect age in Triatoma infestans

“…The simple eyes or ocelli of adult insects have been the subject of numerous anatomical, physiological, and behavioural investigations (reviewed by Goodman 1970, Mizunami 1994, 1995. Different functional roles have been ascribed to these organs, e.g., modulation of muscular tone for the flight system, flight equilibrium control (Wilson 1978, Stange & Howard 1979, Stange 1981, Rowell & Pearson 1983, orientation in walking flies (Wehrhahn 1984) and ants (Fent & Wehner 1985) and, possibly, the dorsal light response used during flight (Kalmus 1945, Goodman 1965.…”

The role of the ocelli in the phototactic behaviour of the haematophagous bug Triatoma infestans

“…Ocelli have been reported to modulate the sensitivity of compound eyes to light. However, the capacity to guide phototactic behaviour by themselves has rarely been mentioned (Mizunami, 1994) or even impossible (Goodman, 1970), based on studies performed in insects exhibiting positive phototaxis. So far as we know, this work is the first analysis of the ocellar function in relation to negative phototaxis and constitutes the first report on that capacity of insect ocelli.…”

“…Different functional roles have been ascribed to these organs, in particular in those insects considered as "good flyers". They include modulation of the muscular tonus of the flight system, flight equilibrium control and the dorsal light response used during flight and also orientation in walking flies and ants (Goodman, 1970(Goodman, , 1981Wehrhahn, 1984;Mizunami, 1994Mizunami, , 1995.…”

The ocelli of Archaeognatha (Hexapoda): Functional morphology, pigment migration and chemical nature of the reflective tapetum

“…Reflective crystal tapeta are relatively common in insect ocelli, for example, in cicadas (Ribi and Zeil, 2015), dobsonflies (Megaloptera), odonates, cockroaches and locusts (Goodman, 1981). Tracheolar tapeta in the ocelli are reported to occur in Diptera (Goodman, 1970), Hymenoptera (Somanathan et al, 2009) and tentatively also Trichoptera (Hallberg and Hagberg, 1986). Thus, despite the present scarcity of data, the presence of tracheolar tapeta in ocelli could be an evolutionary novelty of certain Holometabola.…”

“…Tapetum crystal and screening pigment chemistry Several reviews and textbooks claim that the tapetum is formed of urate crystals in Schistocerca (Goodman, 1970), Periplaneta (Goodman, 1981) and in the 'typical insect ocellus' (Chapman, 1998;Lancaster and Downes, 2013;Klowden, 2013). However, as rigorous tests demonstrating the chemical nature of the tapetum crystals have rarely been performed, our finding of xanthine, which is very similar to both guanine and uric acid, might not be uncommon.…”