Ocelli or “Simple eye”

Apis mellifera with arrow pointing to the dorsal ocelli, the central ocelli is blocked by hiars on the head.

Lasioglossum quebecense male with ocelli circled

The word ocelli is derived from the Latin word ocellus and means little eye. The ocelli are simple eyes that bees use to orientate themselves towards the sun. Located in a triangular shape are two dorsal ocelli and one central ocelli. They are located dorsally on the bees head (see images above for location).

Coelioxys coturnix female with arrows pointing to central and dorsal ocelli

The ocelli are simple eyes, meaning they collect and focus light through a single lens. These simple eyes assist bees with sun orientation so they can navigate well during the day. Some bee species are crepuscular meaning they are active from dusk until dawn. These species have enlarged ocelli which detect minute differences in light and assist in navigation in the dark. One example of this would be a bee living in the desert. With extreme day temperatures it may only be practical for the bee to forage at night. A second example would be pollination of evening primroses which occurs at night by bees or Lepidoptera (Butterfly’s, Moth’s and Skipper’s).

Cerceris sp. with arrow pointing to compound eyes.

Bees also have compound eyes which are the noticeable eyes on the bees head (see image above.) Compound eyes contain multiple lenses or facets which focus light onto retinula cells to perceive an image. These two groups of eyes together allow the bee to navigate by sunlight and with landmarks and add to the information from pheromone markers left by bees. I have included some other images I have of insects showing off their ocelli below.

Coelioxys dolichos male from FL with arrow pointing to ocelli

Triepeolus sp. on Spotted knapweed

Coelioxys obtusiventris female

Written By: Rob Snyder

Rob Snyder has written 66 post in this blog.

I currently work out of the Butte County Cooperative Extension in Oroville, CA as a Crop Protection Agent. I received my B.S. in biology from Delaware Valley College, PA. There I attained a majority of my entomological knowledge from Dr. Chris Tipping and Dr. Robert Berthold. After graduation, I was an apiary inspector for 2 years at the Department of Agriculture in Pennsylvania. In my third year there, I still inspected some colonies but I mainly focused on The Pennsylvania Native Bee Survey (PANBS) where I pinned, labeled, entered data and identified native bees to genus species. Leo Donavall assisted me in learning the basics on positive Identifications of the native bees. Around the same time I began working on coordinating kit construction and distribution for the APHIS National Honey Bee Survey. I was also fortunate to conduct many of these surveys with fellow co-worker Mike Andree and Nathan Rice of USDA/ARS throughout California. All of these experiences have led me to where I am today, working to assist beekeepers in maintaining genetic diverse colonies resistant to parasites while reducing the use of chemical treatments in colonies. The BIP Diagnostic Lab at the University of MD is in an integral part of this process by generating reports in which we can track change and report to beekeepers vital information in a timely manner which may influence their treatment decisions.


19 Responses to “Ocelli or “Simple eye””

  1. Dan Gordon

    Great pictures and really interesting information. FYI, crepuscular means “active during dusk or dawn” not “active from dusk till dawn”. Active from dusk till dawn is “diurnal”.

  2. Dan Gordon

    Opps! I meant to say that active from dusk till dawn would be nocturnal! Dawn to dusk would be diurnal.

  3. CharBee

    do male bees (drones also have Ocelli and have you pictures? All the closeups I’ve seen of the Drone seem to show their huge compound eyes with no room for Ocelli. Does this mean they navigate by assembly of compound sight? Perhaps this is because their main mission is to locate the neighborhood Pickup Bar (drone zone) above the trees?