Monday, March 23, 2015

Floral Visitors 6

Pollinator activity has really been picking up this week, yet I have had limited time to make observations. The weather has been mostly overcast with one storm exiting and another approaching, just as the fruit trees here are coming into bloom. I was lucky enough to observe a few things, even if I wasn't able to photograph them.

A single small plum tree (less than half as wide and as tall as the large tree at my work pictured a few posts ago) has been in full bloom and has attracted swarms of almost every type of insect pollinator. Here's what I could capture on film:

Prunus salicina cultivar with floral visitors

Many of the photos ended up being akin to a searching game, I enjoyed trying to see how many insects were in the photo. The two bees in flight may be obvious, but the solitary bee in the flower or the predatory Scathophaga dung fly awaiting a meal may take some searching...

Social wasp, family Vespidae
 Paper wasp queens are just beginning to emerge from their winter hideouts to start new colonies. Though they do not collect pollen, the adults occasionally feed on nectar and can be quite docile when on flowers. They will often only become aggressive when you approach the nest, they are protecting their young (and if they are the invasive Polistes wasps, I will knock down the nest). Paper wasps feed their young chewed up bits of insects, particularly caterpillars. This can be beneficial in a garden with many invasive moth larvae, but perhaps less beneficial if they are eating larvae of rare butterflies.

I did not get a good look at the face of this wasp, but I concluded it was not a bee from the position it is holding its wings, whereas bees will overlap their wings over their back when they land. Some solitary bees look very similar to wasps. The differences are often only apparent up close.

Butterfly, order Lepidoptera
This individual butterfly was working this tree for a long time, and was even there when I passed by hours later. I do not know what type of butterfly it is, but I'm sure someone does. Every time I moved to the side of the tree it was working, it moved to the opposite side!

Butterfly, order Lepidoptera
While butterflies aren't the most efficient pollinators of this type of flower, they still must account for some pollen transfer. All it takes is for a single fertile grain of pollen to be transferred to a receptive stigma for reproduction to be successful. Besides the butterfly, I also saw a single diurnal moth on the flowers of a small neighboring plum tree, an English sugar plum. I am not sure if the cultivars are compatible, but it is the first other plum to bloom nearby in a long time.

Hover fly, family Syrphidae
Among the Lepidoptera, many members of the order Diptera (flies) were observed on this tree. Small gnats, house flies, and hoverflies were occasionally seen in the flowers. Syrphids (flower flies, hoverflies) are common flower visitors here, and it is my understanding that they eat the pollen. They may imbibe nectar on occasion, but probably only on shallow flowers where the nectar is within reach. Their smooth exoskeletons with only a few hairs compared to bees are not the most efficient at transferring pollen, but they serve other important roles in the garden, one of which may just be as prey.

Rhamphomyia sp. (I think)

One of the most common members of the Diptera in my yard are these dagger flies. This is what I had seen last month on many of the Crocus flowers. Though I have never observed it, they use their long proboscis to eat prey insects, probably other flies (small ones). What I have seen most is that these insects use their long proboscis to probe for nectar, and are serving as pollen vectors in the process.

Scathophaga sp.
This conspicuous predatory fly sits and waits for unsuspecting prey to land too close. I have not seen Scathophaga flies (sometimes called dung flies for the place where they lay eggs) to show interest in the flowers themselves, but instead I watched as they captured smaller flies, and small bees are probably also on the menu. They are sinister creatures, just sitting and waiting until... SNAP! They catch a meal. They posses hairs around their mouth parts, a feature that protects them while they eat struggling prey. So, who wants lunch?

Scathophaga sp. and Apis mellifera
A dung fly nefariously observes a honeybee, yet the honeybee was too large and fast to be caught. Honeybees were all over this tree, though most didn't hang out in the flower long enough for me to get a good shot. It's interesting to me how they will linger on some flowers, and move quickly in and out of others. I suppose this has to do with what they are getting from the flower, either pollen or nectar, and how easy it is to obtain them. They may also linger more in large flowers where they can "hide" while they pack the pollen into their corbicula (pollen baskets). Other times they will pack the pollen while they are in flight.

Solitary bee 
Small solitary bees were literally swarming this tree on the warmest days. Regrettably, I am not yet good enough at identifying them to tell you what they are most of the time. The small bee here was just sitting there, perhaps waiting until the day warmed up before foraging continued. According to the Xerxes Society, about 4,000 species of native bees have been identified in the United States, many small solitary bees smaller than honeybees.

Tiny solitary bee
Many of the small solitary bees are quick to move from flower to flower. They visit the flowers for both nectar and pollen and are very efficient pollinators. A study showed that the presence of solitary or otherwise native bees increased honeybee efficiency by causing them to visit more flowers. While I did not read the study myself (nor can I remember the name of it) this may be in relation to the chemical markers bees leave on flowers. These chemical markers are used so they know which flowers they have already visited, an extremely efficient tactic. As far as total floral visitors in the world goes, bees probably only represent something like around ten percent of the flower visiting insects, yet are one hundred times more efficient and effective as pollinators due to their morphology and behavior.

Solitary bee
A small solitary bee dives for nectar. This species, of which I am oblivious, is the most common of the small solitary bees that I have seen here. I believe this species was also a common visitor to many of the Crocus, and also common on the manzanita (see below).

Megachile leafcutter bee
The extremely quick Megachile leafcutter bees are large, somewhere between a honeybee and bumblebee in size, and faster than any other bee I have seen.

They are ground nesting bees who line their cell walls with pieces of leaves, thus "leaf cutters". Though they are solitary, each female laying her eggs and feeding only herself and her eggs, they will often share tunnel systems with a single entrance.

Besides this plum tree, I have also seen these large bees on the local manzanita and buckbrush (Ceanothus sp.), and I have also seen them buzz pollinating Dodecatheon hendersonii.

Solitary bees on Arctostaphylos viscida
Like on the plum tree, these tiny bees were swarming the manzanita's. They were among other bees, like bumblebees and Megachile leafcutter bees, as well as dagger flies, to feast on the bounty of the ericaceous floral display.

Solitary bees on Arctostaphylos viscida
No less than two small bees worked each flower cluster at a time. The shrubs in the sun flower better, and also are more attractive to pollinators, an observation that appears to be common in the world of pollination ecology.

Muscari armeniacum with a plume moth
Plume moths (family Pterophoridae) have been observed to be highly interested in the grape hyacinths at night. During a brief walk through the garden after work one night (who doesn't do that, am I right?), I saw a moth on almost every grape hyacinth!

In the day, particularly in the afternoon when the large patch of Muscari is lit up by the sun, many honeybees, bumblebees and Megachile bees were attracted to the flowers. Perhaps the warmth of the sun "unlocks" the mildly sweet scent.

Others in the Scilloideae showed to be of interest to some pollinators. Scilla bifolia has been of some interest to a few flies, while moths were nectaring on the Chionodoxa at dusk. Interesting...

1 comment:

  1. Appreciated your comment about the plume moths at nectar on Muscari armeniacum and moths on Chionodoxa. I am finding it difficult to learn much about moths as nectar-seekers at dusk or during the night. It has not been easy to assemble information even about butterfly usage of specific plants. I've been compiling information about these things for years.


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