Saturday, April 11, 2015

Floral Visitors 7

The weather this week has been fairly drab - overcast with nighttime lows nearing freezing. Bees have had little opportunity to forage, and my daughter and I have been sick so my opportunities to observe and photograph floral visitors has also been reduced. Nonetheless, I keep my camera with me almost all the time, so if an opportunity arose, I would (hopefully) be able to capture it.

Lomatium utriculatum

Flies have been the dominant floral visitors this week, well adapted to coping with adverse climatic conditions. They are apparently unbothered by cold and wet, possibly even appreciating the lack of competition or even perhaps predatory distractions. Contrary to the popular belief that flies are attracted to putrid smelling flowers, they are attracted to sweet scents as well. In some cases the smell of rotting flesh (like in some of the aroids) attracts flies who wish to lay their eggs in rotting materials (logs, leaf debris, etc.) or dead animals. Upon landing on a repulsive smelling flower, adult flies inadvertently serve as pollinators, wandering around the putrid inflorescence looking for a place to lay their eggs, and spreading pollen as a result.

Lomatium utriculatum
Flies are considered generalist pollinators, and are attracted by a wide array of floral characteristics. Some eat pollen, some drink nectar. "Fly flowers" in the United States are typically shallow and small, meaning that the nectar doesn't require a long proboscis to reach it. Many flies, as well as beetles, have fairly short probosces so can only feed on this kind of flower. Many flowers in the Apiaceae, or carrot family, have this type of flower and are often visited by a variety of flies. Many fly flowers are white or yellow, but some are green or brown. Sometimes there is a detectable scent, sometimes not.
Lomatium utriculatum with Rhamphomyia sp.
A few dagger flies and some other flies were visiting the flowers of the fine-leaf desert parsley. The small yellow umbels are the first of the Lomatium's to flower in my yard, growing on open banks consisting of deficient alluvial soil. Ants and tiny gnats also visit the tiny flowers (only reaching around four inches in response to the local climate), but the gnats are more common when the weather is nicer. This is one of the species that inhabits Upper Table Rock.

Alyssum montanum
Colloquially known as harvestmen, the arachnids of the order Opiliones are separate from  spiders (order Araneae) by their fused body regions and single pair of eyes. I'm not sure what this one was doing on these flowers. I doubt it was interested in the floral rewards (nectar or pollen), but possibly for the solar radiance. Flowers sometimes reflect heat from the sun, a feature that attracts some pollinators or entices them to visit the flowers.

Ranunculus occidentalis
I spotted this beetle easily on the bright glabrous yellow flower of the buttercup. Beetles are mostly pollen eaters (though a few visit flowers for nectar) or are there to eat the flower itself. Many beetles are attracted to flowers as a safe haves, wither to mate or to spend the night in relative safely from predators. This one was there for the pollen, its mandibles at work. The study of beetle pollination is complicated, it is often difficult to tell if a beetle is eating the pollen or the flower itself. There have been cases where the flower eats the flowers, yet they still set viable seed, suggesting they are the pollinators of those flowers. Peculiar.

Sanicula crassicaulis
I have seen this understory forest herb on a variety of occasions, and every time there have been ants on the flowers. This small carrot relative grows to under a foot tall with a six inch spread. The tiny flowers are less than a eighth inch, 3 or 4mm perhaps. I am not well read on ant pollination, only having read once that their bodily secretions have shown to sterilize the pollen of some plants. Other roles that ants play is by protecting plants from certain pests, like mites or other sap suckers. Many plants in the Rosaceae (rose family) attract ants to them by providing the ants with nectar from "extrafloral nectaries", small excretory organs found on parts of the plants besides the flowers (sometimes at the leaf axil) that produce a sugary nectar-like liquid.

Laurus nobilis
Laurus nobilis
This bay laurel, or something close, was appropriately growing in front of a local pizza shop in Rogue River, Oregon. The shrub was trimmed to a hedge, and there were only a few flower clusters, but I watched as this fly visited several flowers. The plants are documented as being dioecious, having male and female flowers on separate plants. This plant appears to be a male, having filaments and anthers, though I did not see any pollen shed. Perhaps rain had washed it away? Nectar is secreted at the base of the ovary and seeps through the space between the petals and the ovary. That's what the fly was after.

Aucuba japonica, female
Though there are no bugs in this picture, I assure you flies were there! The Japanese spotted laurel, Aucuba japonica, is a common sight in shaded gardens here. The plants are dioecious, meaning female and male flowers are borne on different plants. This one here is a female, notice the flowers are lacking anthers. They do however provide nectar, a sweet smell emanated from the plant (though with my congestion I was barely able to detect it!). The plants can grow to an excess of eight feet, but the flowers, emerging at the branch tips with the new leaves, are a meager half inch (and that is a generous estimate).

Now see Floral Visitors Pt.2


  1. Thanks Travis for the ant on Sanicula crasscaulis / Pacific Snakeroot photos! For 15 years I have been stewarding Seattle's only natural colony of this species, weeding around plants, as the colony has spread in apparent reaction. I have always wanted to know who pollinates them, and who uses them in general. With no evident petals, the flowers don't look like they are designed to attract the better known pollinators that may be attracted to a color display from a distance, so ants, attracted to a scent make sense!

    1. Thanks Stewart! I always appreciate your input. The flowers do indeed have petals, but they are curved in much like the Lomatium, while the anthers and stigma project out beyond them. I'm hesitant to call the ants the pollinators, without exclusion tests and seed viability compared with open pollinated and bagged plants there is no way of knowing for sure.


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