Archive for the ‘predator’ Category

Mimics of bumble bees

July 11, 2011

Syrphid fly, Mallota bautias

We think that we know what a bumble bee looks like, but often we are deceived by some very good imitators. There are a number of flies that masquerade as bumble bees despite the fact that they have only two wings, instead of four and that their antennae are significantly shorter. There are even a few moths and beetles that imitate bumble bees.

Syrphid fly, Mallota

Syrphid fly, Eristalis

Flower flies, also called hover flies or Syrphid flies visit flowers frequently and are good imitators of bees or wasps. They lack stingers, but their appearance gives them some protection from hungry birds that fear the sting of a bee and are left alone. Some are specialized to look like bumble bees. This mimicry occurs in other continents, too, with European and American flies mimicking European and American species of bumble bees respectively.

Robber fly

Robber fly, Laphria thoracica

Robber flies are ferocious predators, capable of catching some insects in flight. Among them, there are some that imitate bumble bees so convincingly that they can fool anybody, including experts. In this case, the purpose of the mimicry may be to fool their prey, as well, as their possible predators.

Bee fly, Bombylius. Notice the long tongue

Carpenter bee on swamp milkweed

Some beeflies and also tachinid flies are good mimics of bumble bees.

Carpenter bees also look very much like bumble bees. The main difference is their glossy and almost hairless abdomen, while bumble bees are covered by fuzz all over. In this case the mimicry would benefit both of them.

Cuckoo bumble bee, Bombus citrinus

Curiously enough, some species of bumble bees are mimics of each other, although they may not be closely related. Some of the cuckoo bumble bees seem to be mimics of their hosts, for instance, Bombus citrinus and its host Bombus impatiens.

Bombus impatiens

The mimicry makes it very hard to tell the species of bumble bee apart. The similarity among bumble bee species probably provides them additional protection. Predators need to learn the lesson only once instead of twice. In fact, this kind of mimicry may help the males, also, since they lack stingers.

Bumble bees. Introduction

Beginners Guide to Pollinators and Other Flower Visitors


Bumble bee’s enemies

July 10, 2011

Bombus bimaculatus paralyzed by ambush bug

The life of a pollinator can be quite hazardous. There are plenty of creatures willing to devour one of them, from insects and spiders to birds. In addition to that, there are many parasites and other pathogens. Perhaps the highest mortality comes from the so called parasitoids and cuckoos. Parasitoids behave somewhere between a parasite and a predator; they parasitize the host, feeding on it, and eventually killing it, while predators kill and eat the prey all at once. Cuckoo bees and wasps, just like cuckoo birds take over the nest, lay their eggs and let the workers of the host species take care of the brood. Many cuckoos are related species, mainly other bumble bees; in some cases they mimic the appearance of the host species.

In general, most birds seem to avoid bumble bees; although there are a few species that specialize on bees. Skunks, voles and moles can attack their nests and eat their reserves and grubs. These creatures destroy a good number of nests. There is a story about Darwin saying that the British armies owed a lot to old spinsters. This was his explanation: Old spinsters owned cats which ate field mice. Fewer mice meant that more bumble bee nests survived. In turn, the bumble bees pollinated the alfalfa that fed the cattle that fed the soldiers and kept them strong and healthy. It was just an unproven entertaining hypothesis, but still a nice illustration of the intricate web of life.

Crab spider on thistle

Crab spiders are so called because they look and move like crabs. They are among the most common predators. They build no webs; instead they hide inside blossoms, waiting patiently for prey and ready to pounce on the first flower visitor that comes within reach. They are well camouflaged and are capable of changing their colors if they have to move to another flower.

Ambush bug on multiflora rose blossom

Ambush bugs deserve the name. They sit for long hours, well hidden inside a flower or cluster of small flowers, waiting for flower visitors. Their contour is jagged making it hard to detect them. They are very good at holding still, tucked in between petals. Their front claws look like those of a preying mantis and they have a sharp beak used for stabbing their prey and sucking vital juices. Their venom must be very powerful because they can paralyze a bumble bee twice their size in the blink of an eye.

Conopid fly on common milkweed

Some flies of the Conopidae family parasitize bumble bees. They hang around flowers waiting for bumble bees and lay just one egg in the narrow space between body segments. The egg hatches, the larva gets inside the unfortunate bee and proceeds to feed on its blood, (its real name is hemolymph because it is more similar to lymph than to blood). As it grows it starts eating the tissues, eventually killing the host.

Bee wolf Philanthus gibbosus

Bee wolf wasps attack many types of bees, bumble bees included, and also other insects. They overpower them and take them to their nests to feed their young. They have a very thick, pitted body cover that serves them as armor.

cuckoo bumble bee, Bombus citrinus

Other enemies of bumble bees are bumble bees themselves, the so called cuckoo bumble bees. There are several species of them. They build no colonies, nor have any workers. A queen attacks and subjugates a colony of honest, hard working bumble bees. She usually kills the resident queen and destroys any eggs. Then proceeds to lay eggs of her own which are nurtured by the workers of the host species.

Bumble bees also suffer from many of the pathogens that afflict honey bees, such as mites, fungi, nematode worms, bacteria and viruses. The life of a pollinator is not an easy one.

Bumble bees. Introduction

Beginners Guide to Pollinators and Other Flower Visitors

Ambush bug

April 30, 2011

Jagged ambush bug

Poor pollinators! They have to contend with dangerous creatures hiding among the petals of the flowers, not just crab spiders but also sinister ambush bugs. The name is well deserved. These bugs are very good at hiding and waiting patiently until a bee, a fly or some other flower visitor comes near. Then, swift as lightning, they impale their victims with their sharp beaks loaded with fast acting venom. In addition to this form of attack, they have powerful spiny, enlarged front legs that spring into action catching the hapless victim. Just like crab spiders they don’t chew their preys, they drink the fluids and drop the dried up husk down when done feeding.

Ambush bug and prey, a large bumble bee

Ambush bugs are usually smaller than many bees and bumble bees, which doesn’t prevent them from catching them. They have a very unusual shape, with protruding, pointy parts. The rear end is wider than the front. The color pattern is broken. All this makes it hard to see their contour and contribute to their camouflage.
The males are considerably smaller than the females. Sometimes they ride on a female, when mating and don’t hesitate to take food from them.

Habitat. Practically all the habitats visited by all the flower visitors mentioned in this guide. Everywhere where there are flowers.

Season. Most common from July to October. In southern states, also found from February to December

Flowers. A vast array of flowers, usually those grouped in clusters likely to attract many visitors; they like flower heads with many florets that makes it easy for them to hide: goldenrod, asters, queen Anne’s lace, sunflowers.

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Crab spider

April 26, 2011

Whitebanded Crab spider on thistle (Misumenoides formosipes)

Not all flower visitors are insects and not all are pollinators. In fact, some are a threat to pollinators. Such is the case of spiders, crab spiders in particular. The name is very appropriate: they look and they move like crabs. They are very adept at hiding between petals and waiting patiently for prey to fall right in their clutches.

Whitebanded Crab spider hiding on goldenrods

They are not very discriminating; any flower visitor will do. Bees of many kinds, as well as flies and butterflies and even beetles fall prey to them. They are capable of overpowering creatures bigger than themselves. With their fangs they inject saliva, rich in enzymes that act the way a strong acid would, dissolving the tissues of the victim. Spiders can’t chew solids, so they take this “soup” instead.

Crab spider and prey, a small bee

A different type of crab spider and honey bee

Female crab spiders come in different colors. Usually they match well the color of the flower where they are hiding.

Goldenrod Crab spider (Misumena vatia)

It is said that they can change coloration if they move to another flower of a different color and that this change takes several days. Males are a lot smaller and have thinner abdomens. They are not seen very often.

Habitat. Sunny fields, gardens.

Season. From April to October. Practically year round in southern states.

Flowers. they prefer flat open flowers, especially in the Asteraceae family. Asters, thistles, sunflowers, goldenrods provide just the right kind of hiding places.

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Bee flies

April 9, 2011

Bee fly, Bombylius, on spring beauty

Another type of fly that is commonly found at flowers is the bee fly, Bombylius, frequently seen in the spring. It is furry like a bumble bee, but smaller. You can distinguish it from bumble bees by its enormous eyes and very thin legs. It is plumper and hairier than the syrphid flies, so it is easy to tell apart. It has a sharp and rather long tongue or proboscis which it dips in the heart of flowers in search of nectar (they, especially the females, take pollen in addition to nectar). It flies mostly in early spring, around the same time that Andrena bees are most common; it does so because it lays its eggs near the nests of these bees. Its larvae parasitize the nests of Andrena (it also parasitizes other bees such as halictids and colletids). Despite this bad habit of exploiting other pollinators, it is a good pollinator itself.

Bee fly probably searching for Andrena bee nests

Habitat. Woods (in early spring when trees are still bare) and meadows. It is seen flying low over bare ground. Throughout all of North America.

Season. Primarily early spring but it can also be found as late as October and even November.

Flowers. Early spring flowers such as spring beauties, later in the season many other flowers including asters. It prefers flowers with a deep throat which it can reach with its long tongue.

See also:
Pollinator of the month. Bee flies

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