Thursday, April 7, 2016

Ye Olde Prunus

Andrena sp.
Observing the old plum in my yard, I am again astounded at the diversity of floral visitors it attracts. Aside from the obvious honeybees (my hive is places close to this tree), a number of other pollinators visit fruit trees. I was only able to observe for about a half hour, such free time is something of a luxury for me as a parent, yet in that short period I photographed at least thirteen different species of flies, bees, and beetles, and I imagine that if I had an entire day to sit and watch that number would be doubled if not tripled.

Honeybees love the fruit tree bloom
Honeybees are a given. My hive is situated close to this tree, but fruit trees tend to attract honeybees wherever the hive is. Fruit tree honey is supposedly of good flavor, though I have never collected honey this early, so this ends up feeding the bees.

Flies, perhaps Tachinidae in the foreground
There were two prominent groups of pollinators during my brief observation. The first were bees, mostly Andrena with some honeybees (and a few species of Nomada, I think), and a single bumblebee (not pictured). The second group were the flies. They were very numerous, rivaling the bees in quantity, but they don't seem to visit as many flowers as the bees and are less active while foraging, unlike bees which are in nearly constant motion. Flies mostly feed on the pollen, particularly the "short tongued" flies.

Empis sp.
The exception to the pollen-only diet appears to be the dance flies, family Empididae. Their long proboscis is perfect for plunging into the calyx of a flower to imbibe the nectar. I have observed the larger dance flies visiting a variety of flowers, native and otherwise, in search of nectar. Aside from flowers, they feed on other flies, even smaller dance flies.

Syrphus opinator
There were, of course, a variety of syrphid flies. This species is one of many that seeks plants with aphids to lay eggs. The larvae feed on the aphids, killing more than it can eat, while adults feed on pollen and occasionally nectar. Their mouthparts are very short, so they can only feed on nectar where it is very accessible such as on very shallow flowers. Many herbs in the carrot family are of use here, as well as many in the Asteraceae (sunflower family).

Syrphus opinator
Many syrphids are bee or wasp mimics, probably an evolutionary tactic to avoid being eaten. They can be differentiated from bees by their stubby antennae, having only two wings, and no pollen-carrying apparatus. Bees, conversely, have relatively long segmented antennae, four wings, and usually either scopae or corbicula to carry pollen.

Syrphus opinator 
Eristalis dimidiata
Another syrphid, this species in known as the drone fly. Adults feed on flowers, pollen and nectar. Larvae are found in stagnant water. They have the lovely "magic reappearing lunch" name of rat-tailed maggots, so named for the tail-like "snorkel" they use to breathe. They tend to prefer water with a lot of algae and other small organisms, on which they feed. These waters are often high in nutrients, and subsequently depleted of oxygen where it is shallow from all the algae, etc. As if you didn't need more reasons not to drink stagnant puddles out in the wilderness, the eggs of some species of Eristalis can be swallowed by humans and the developing larvae will live in the intestinal tract, a condition called myiasis (a term used to describe any parasitic fly larvae infestation of the human body).

Platycheirus sp.
Platycheirus is an obscure genus of syrphids, mostly because they are usually difficult to find if they are sought. To be sure, this photo was completely accidental and involved luck and chance more than skill. This is mainly a group of pollen feeders, and what is peculiar is they are cited as feeding primarily on wind pollinated plants such as Plantago, Poaceae (grasses), Cyperaceae (sedges), and Juncaceae (rushes), all of which are abundant here. They also feed on plants like Ranunculus and Daucus, surely others, according to BugGuide. Larvae feed on aphids.

Scathophaga sp.
Not a syrphid, but a predatory fly whose larvae feed on other fly larvae within animal feces or perhaps decaying vegetation. As adults they feed on other flies and other insects. I have never seen them inside of or feeding on flowers, but appear to be ambush predators.

Andrena, Scathophaga, and a dance fly (Empididae)
Andrena sp. (top) and Coccinella septempunctata (seven-spot ladybird, bottom)
Andrena sp.
Bees were numerous, outnumbering all other floral visitors. They were, however, the most difficult to photograph as they would just move to the other side of the tree no matter how silent or slow I thought I was. The most numerous bees were one or two species of Andrena, small digger bees common to grassy areas and lawns. These small bees are perfectly adept at crawling inside the flowers to get the nectar.

Andrena sp.
Andrena and Empis
A lone yellowjacket (Vespula sp.) seeks nectar
Toxomerus occidentalis
A neighboring peach tree, Prunus persica, is related to plums but has larger flowers. Unlike the aging plum, my peach trees are newly planted last year. Toxomerus, another syrphid, lays its eggs singly on the leaves of aphid infested plants. The larvae are destroyers of aphids, then move into the soil to pupate. This is a good reason not to cultivate soil excessively, or at all.

Toxomerus occidentalis
Maybe this year I'll get some fruit! Despite loads of pollinator visits to these trees, fruit set has been low. This could be lack of cross pollination. There are two other plum trees, but they are rather young and don't flower prolifically yet.


  1. Native pollinators are familiar with crab apple flowers. It seems that this is why they readily accept apple blossoms. It also seems that plum, cherry, pear and a few other flowers are equally similar and acceptable.
    I have patiently observed daffodils, lesser celandines and forsythias and here the story is quite different. Hardly any pollinator stops by.

    1. Agreed, but sometimes I'm surprised and that's when it gets exciting. Yesterday I observed various bumblebees visiting Narcissus 'Thalia' (a N. triandrus hybrid), Epimedium, and Symphytum. Exotics give us a chance to test the theory of pollination syndromes, or to challenge them.

  2. You are an amazing photographer! Love seeing all those pollinators.


If leaving a comment as "Anonymous," please leave your name or contact information.