Saturday, April 23, 2011

Microcosmos Cactus Flower

Engelmann's Prickly Pear, Opuntia engelmanni 
Engelmann's Prickly Pear is the most widespread and common Opuntia around Tucson, and it's just starting to bloom. The flowers are beacons for photographers and pollen and nectar seeking insects. They are flat and easily approachable for bees with short proboscis and even unspecialized beetles.
 Carpophilus  sp.
 In the morning, when fresh flowers open, countless  Nitidulids of the genus  Carpophilus  arrive. They 'drop out of the sky', land and slip between the petals, where they congregate, feed, and find their mates. 

I used to think that they are specialized on cacti, but I this week I found clusters of them in Apache Plume (Rosaceae) and in Arizona Thistle (Asteraceae) in Florida Canyon where the cactus flowers were just budding.

Lasioglossum sp.
 Bees of all sizes are visiting. This small, partly metallic one will hopefully be identified by Monday. 
P. s Thanks to John Asher on Bug Guide: he identified the genus as Lasioglossum.

Cactus Bees,  Diadasia sp.
Cactus Bees, genus Diadasia hectically buzz from flower to flower and dive deeply between the stamina. Males refuel with nectar, females collect pollen for the brood in addition. Often, before they fly off again, they seem to hesitate and wait motionless. That's the moment when males will suddenly pounce on the females.

So this is how the Diadasia couples meet. They share their dating grounds with many other hopefulls. Just check out the depth of the flower behind them, the red and black wing pattern belongs to one of the beetles below

Clerid beetles Trichodes ornatus
Clerid beetles Trichodes ornatus come, like the cactus flowers, in red and yellow. But they don't have to match their back ground - the red ones look deceptively like a blister beetle that flies at the same time, the yellow ones imitate wasps.

The two color morphs occur equally among the larger females and the small males, and there seems to be no mating preference related to color. Still, three is a crowd.

Bruchid Mimosestes amicus
Bean Weevils can be found in cactus flowers but they may just be resting while searching for leguminose flowers where they lay their eggs.

Listrus, a dasytin Melyrid
Dasytinae forage wherever there is a lot of pollen. With their dense hairy coats they make good pollinators.

Where so many insects come together predators will also hang around. Here is one predator stalking another. But the little jumping spider did not attack the tiny Attalus, his aposematic colors  may have warned her off.

Staghorn Cholla Trichopuntia versicolor

Prickly Pear Cacti (Opuntiae) and their close relatives, the Chollas (Cylindropuntia or in older literature still also Opuntia) dominate our Sonoran desert with an abundance of species. Every day seems to bring new color schemes. But the flowers are all very similar in their simple architecture and they are visited and pollinated by the same army of insects.


  1. So educational and such great photos... thank you!

  2. Especially like the pic of Staghorn Cholla with sun shining thru petals.

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