The final chapter of the Year of Pollinators series focuses primarily on beetles (order Coleoptera) as well as other arthropod floral visitors that I have encountered this year. In general, beetles and other arthropods are much less significant than bees, wasps, flies and butterflies. However, this strongly depends on the plant being visited as there are for example there is at least one species in 34 families of plants that is pollinated primarily by beetles (
Bernhardt 2000).
Thrips have even been regarded as pollinators of some plants, though their role as true pollinators is controversial (I have seen them on flowers such as
Calendula, although their motives and effectiveness was uncertain). Other insects also play important roles, or are just common among flowers. I hope you enjoy it!
(Also see
Pollinators of 2015 posts:
Bees,
Lepidoptera,
Wasps, and
Flies)
Order Coleoptera
The order Coleoptera includes all true beetles and weevils. Coleoptera is from the Greek word
koleópteros (κολεόπτερος) which literally translates to "sheathed wing" in reference to the hardened and thickened forewings that cover and protect the more delicate hind wings. Due to their robust nature, they are well represented in the fossil record and suspected to be the earliest pollinators, though this is a biased theory which I think is skewed due to the fragility and poor representation of other fossilized pollinators. Beetles have millions of years on bees and wasps, according to the oldest fossils of each ever found. The oldest beetle fossils were something around 300 million years old (
Benisch 2010) while the oldest bee fossil was a mere 100 million years old (
Handwerk 2010). However, the oldest record of an insect fossil bearing angiosperm pollen dates to around 100 million years old on the bodies of six female thrips preserved in amber (see:
First ever record of insect pollination from 100 million years ago). Regardless of which insect was the first pollinator (maybe they all were first together), beetles are nonetheless important.
As pollinators, they tend to prefer open flowers with easily accessible nectar and ample pollen. Color doesn't seem to matter as much as the shape, which is more often than not large and bowl/cup-like (like
Magnolia,
Liriodendron, some
Tulipa). Smells can range from musky-sweet to fetid to having no smell. Most beetles are opportunistic and will browse whatever they please, often eating parts of the flower as well. Besides visiting flowers to eat, they often congregate on some flowers to mate or to take advantage of the solar radiance (or in the case of flowers that close at night, to sleep). Even herbivorous beetles can act as pollinators, and there is speculation that certain flowers have evolved to be partially eaten while still producing viable seed (after the beetle pollinated the flower).
Family Buprestidae
This family is known collectively as
jewel beetles because of the metallic iridescence of many of the taxa, though the species I encountered was hardly representative of the potential beauty of this family. In general they are wood-borers, or rather the larvae are, though some also bore through roots, stems, and leaves of a range of plants including grasses. Though they are mostly wood-borers, most tend to only feed on dead or dying wood while fewer feed on green wood.
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| Anthaxia inornata on Iris chrysophylla (April) |
From the Latin ōrnātus, the epithet is a reference to the undecorated appearance of this species compared with the better known members of the family. This species is suspected as being a borer in coniferous trees, which are in no short supply here (Pinus, Pseudotsuga, and Juniperus are virtually everywhere).
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| Anthaxia inornata on Fragaria vesca (April) |
These beetles have appeared on a variety of flowers early in the year (as early as March) on
Narcissus,
Fragaria, and the native
Iris chrysophylla. I have seen them mating on
Achillea millefolium and
Berberis aquafolium. In most cases they seem to aggregate on flowers, suggesting that aside from feeding on the flower parts (and perhaps some nectar or pollen) they are seeking mates.
Family Dermestidae
Considered pests in homes for their potentially destructive habits of eating certain fabrics, including clothing and carpets, as well as museum artifacts.
Carpet beetles (or sometimes
skin beetles) feed on dried organic materials such as animal carcasses and plant materials, as well as the larvae of Hymenoptera and Araneae (spiders). Small species frequent flowers as adults to feed on pollen or nectar. Some dermestid beetles feed on dried skin from animal carcasses, and are part of Nature's
clean-up crew. Because of this, they are often utilized to clean skeletons for taxidermists or museum specimens as they will leave the bones clean.
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| Anthrenus lepidus (?) on Prunus (April) |
Anthrenus includes perhaps 200 species, 18 in the United States. The adults are typically very small and of little concern as pests. However, the larvae of most dermestids are considered destructive to organic products and materials, as well as feeding on fallen pet hair/shed skin from pets and humans (an incentive to keep the house clean, I suppose). Most larvae feed on dead animals, while adults are common on flowers, but their small size (4 mm or less) makes them unlikely to be seen unless you are very close and observant. The species of the beetle in this photo is a guess, since the colored scales of the some species tend to rub away as they age showing the black elytra (shell-like forewings), and since I identified it by the pattern I could be wrong. A better resolution photo would be good.
Family Cerambycidae
The long antennae of the males in this group give them the common name Long-horned beetles. Most of the larvae are tree-borers, but most only feed on dead or dying wood, sometimes decaying wood or roots through the soil. Most adults are flower feeders, though some species eat the plant parts themselves (sap, leaves, flowers, bark, etc). A few species do not eat as adults but only drink water, mate, and die in a matter of days or weeks after pupation. Males tend to have very long antennae, occasionally longer than their bodies, while the antennae of females are usually short.
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| Brachysomida bivittata ♂ on Ranunculus occidentalis (April) |
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| Brachysomida californica ♀ on Wyethia (May) |
Brachysomida is a variable genus with members ranging from black (sometimes iridescent), having brown legs or elytra, or striped. They tend to have a marked preferance for yellow flowers, sometimes white, and they are often composites (Asteraceae). Though my photos of these two species weren't clear enough to give an expert entomologist the confidence to ID them, I identifies the two by their body shapes and the presence/absence of fine hairs (
B. bivittata is hairless while
B. californica is covered in fine translucent hairs).
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| Molorchus longicollis mating on Prunus virginiana (April) |
Molorchus were all over a small stand of chokecherry, a proverbial orgy on the dinner table as they all mated and feasted until they died. These are small beetles with much reduced elytra, the males have antennae much longer than their bodies (see photo below). Larvae are wood-borers of hardwoods and woody shrubs. Due to the tiny forewings, they probably require a humid environment to keep their delicate hind wings from desiccating. This stand was dense and located close to the seasonally river-like Evans Creek in Rogue River, OR.
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| Molorchus longicollis ♂ on Prunus virginiana (April) |
Besides feeding on the chokecherry, I have also seen them on Pacific ninebark (
Physocarpus capitatus) and
Salix.
Family Coccinellidae
The family of
lady beetles (ladybugs, ladybirds) is very large, containing around 6000 species worldwide. They are much more diverse than the typical
red-with-black-spots, with species ranging from striped and blotched in colors ranging from black and white (or solid) to yellow, orange, and even iridescent blue. Most are considered beneficial, and frequently sold as bio-control agents to fight aphid infestations. The larvae are aphid predators, as well as many of the adults, though some species are herbivorous in the adult stage and can become pests when their populations are large (due to a lack of predators).
Many gardeners are unsure of how to properly utilize these insects, either bought or preexisting. The best advice is to stay ahead of the problem by creating an environment (both macro and micro as in a garden setting) which encourages biodiversity. The best way for a gardener to do this is to have a wide variety of flowering plants. By doing this the gardener is providing both shelter (by shading the soil) and resources (pollen/nectar) for beneficial insects and will hopefully encourage them to first become enticed to visit and second decide to stay and mate. I have not yet found the need to purchase ladybugs since I have helped create the conditions that they require. They are small insects with short tongues, so they prefer flowers with easily accessible nectar. Some examples are: almost anything in the
Apiaceae (carrots, coriander, dill, parsley, fennel, etc.),
Achillea,
Alyssum,
Calendula,
Fagopyrum (buckwheat),
Lotus,
Taraxacum,
Trifolium (clovers), and many others.
If, however, there is already an aphid infestation I recommend the following (passed down by a fellow gardener): Place the purchased ladybugs in the refrigerator (do
not freeze them) overnight. Early in the morning, shake them out below the plant(s) which are infested. As the sun rises and the air warms the ladybugs will climb the plant, eating as they ascend, to warm up before they can fly away. If done correctly the plant(s) will be free of aphids.
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| Coccinella septempunctata on my arm (March) |
The seven-spot ladybug is an Old World species repeatedly introduced into the United States for bio-control, and is most likely the species sold in bags in American nurseries everywhere. If at all possible, provide food sources for native lady beetles first instead of introducing more non-native insects, no matter how beneficial.
Family Chrysomelidae
Leaf beetles are a huge family (over 60,000 taxa worldwide) and are varied in appearance and lifestyle. They all seem to eat plant parts, including pollen, while a few are serious pests.
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| Diabrotica undecimpunctata on Narcissus (March) |
The genus
Diabrotica is one of the better known members of the family, being serious crop pests in the southern half of its range (from Southern Canada to Central Mexico). The larvae eat the roots of many Southern crops, one of which is cucumber, giving it one of its common names: cucumber beetle (which is shared with the genus
Acalymma of the same family). While the adults eat plant parts (particularly flower parts) they may contribute as pollinators though they do not move between flowers frequently. They may, however, be useful in flowers that can be pollinated by their own pollen. These small beetles, a little smaller than the common seven-spot lady beetle, have been seen on:
Anemone,
Daucus,
Narcissus,
Taraxacum, and many others. They do not seem to congregate as other small beetles do and instead visit flowers for both food and shelter. I have observed their preferance for large open flowers that either close at night (
Anemone) or give some other form of protection (as was the case with the trumpet daffodils). In my Oregon garden, their presence is benign.
Family Scarabaeidae
Perhaps one of the most pop-culture-familiar families, the
Scarab beetles have been brought to celebrity status by their embellishment into ancient Egyptian artifacts. They are, however, a diverse and widespread group which plays many important roles. The larvae of most feed on dung or carrion, or other decomposing matter such as leaf litter. A few are agricultural pests that feed on roots of live plants. Adults also have diverse feeding habits depending on the species, from feces, dead animals, or fungus to fruit, sap, floral rewards, or other plant parts. Adults sometimes hibernate over Winter by burying themselves.
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| Trichodes ornatus on Eriogonum (May) |
Trichodes, or
checkered beetles, vary in color from red to yellow, often with black. The
ornate checkered beetle,
Trichodes ornatus, is a widespread species West of the Rockies from sea-level to ten thousand feet or more. They are social parasites of bee nests, particularly the family Megachilidae (i.e.
Osmia,
Megachile) and perhaps other bees (including
Bombus) and wasps. They somehow infiltrate the nest and lay eggs, larvae feed on the hymenopteran larvae. If for some reason they cannot eat the bee larvae, they can develop on a diet of pollen, though this lengthens the time to maturity. As adults they seem to have a preferance for white (or perhaps yellow) flowers. Their size (comparable to a honeybee) and hairiness are likely to contribute to pollination.
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| Trichodes ornatus on Daucus (June) |
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| Pleocoma ♂ |
Pleocoma, otherwise known as
rain beetles, do not visit flowers because the adults don't have functioning mandibles and the esophagus is closed off. Adults do not eat, instead the larvae feed on plant roots of specific host plants deep in the soil. Little is known about the larval stages of many species, but some take up to 13 years before reaching adulthood! Females don't fly (because they don't have functioning wings), but emit pheromones that attract the winged males. Specific conditions are required for the adults to emerge, the majority of their lives is spent underground. As the name suggests, they emerge in Autumn or Winter at the onset of rain or snow, depending on the species. After finding mates and laying eggs, the adults presumably die after mating, but to be honest I haven't found any sources explicitly claiming that to be the case.
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| Pleocoma ♂ |
Family Meloidae
This family is known as the
Blister beetles from the blister-causing agent they secrete from their bodies. If touched or squashed, they exude hemolymph (analogous to blood) which contains an odorless colorless terpene called cantharidin. On contact, it causes cellular disintegration (loss of cell-to-cell adhesion) resulting in a blister. Ingestion of a beetle would probably be fatal, and can even kill livestalk who eat hay or straw with beetles in it.
Meloidae larvae are parasitoids of other insects. Eggs are laid in a variety of places depending on the species, sometimes on plants or in/near a host (bee) nest. Larvae hatch with well-developed legs and antennae and move into the host nest. They then utilize the provisions and larvae of native ground nesting bees (such as those in the families Megachilidae and Andrenidae). Several taxa (including
Epicauta, below) utilize grasshopper eggs.
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| Epicauta puncticollis (?) on Hypochaeris radicata (June) |
Epicauta are very common here in the warmest months, feeding on flowers. They were most common on the pungent flowers of
Madia elegans (
see this post), even during the day while the flowers were closed. They appeared to feed on everything the flowers offered, from pollen and nectar to the flower petals themselves. While they appeared to prefer yellow flowers, I had also seen them on the purple flowers of a local
Monardella.
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| Epicauta puncticollis (?) on Madia elegans (June) |
Nearly every closed flower of
Madia elegans (only open in the early morning) had a blister beetle on it. The beetles fed on the floral resources as well as the ray florets, yet nearly every flower produced a plethora of seed.
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| Epicauta puncticollis (?) mating on Daucus carota (July) |
After the
Madia had faded, the beetles were common on the nonnative
Daucus which is the last large-scale bloom of the year.
Family Melyridae
Soft-winged flower beetles are a common sight on flowers, as the name might suggest. What I didn't expect to learn is that they are in fact predaceous in both larval and adult forms, feeding on other insects. Larvae are commonly found in or on soil, under leaf litter, or under bark. Aside from insects, adults feed on pollen and perhaps the flowers themselves to a degree.
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| Listrus on Narcissus (March) |
One thing I have noticed is the soft-wing flower beetles propensity to form an aggregation on or in flowers. This photo, for instance, shows at least six of the small spotted beetles inside this single daffodil, whereas the neighboring
Narcissus were devoid of all insect life (
Narcissus are generally unattractive to pollinators outside their native ranges). It appeared as if the insects were using the flower as a shelter from the elements, and perhaps eating some of the pollen.
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| Dasytinae beetles (Listrus?) on Convolvulus arvensis |
The hairy bodies of these small beetles certainly increases the likelihood that they could spread pollen. Another probability is that they meet in or on flowers to mate.
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| Dasytinae beetles (Listrus?) on Convolvulus arvensis |
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| Dasytinae beetles on Apocynum androsaemifolium (June) |
Few pollinators visit dogbane (I have once seen a honeybee visit a single plant late in the season), though these beetles appeared to be enjoying the available resource. Unfortunately a browsing deer had eaten the plant down to the ground so I was unable to verify if the encounter had enabled seed to be produced.
Order Dermaptera
Besides beetles, there were other floral visitors this year, as in previous years.
Earwigs in the order Dermaptera (probably
Forficula auricularia, the common earwig) are omnivores whose diets include various stages of plant and animal waste as well as living plants and their secretions. They are mostly nocturnal, preferring cool and dark conditions. Despite popular misconception, they do not lay eggs in human ears, and they do in fact have wings (
here's your proof). They do a lot of
behind-the-scenes work in the garden, and I believe their presence would be missed if they were gone.
I've seen them on many flowers after the sun has gone down. They feed on nectar. The plants I've seen them visit are:
Chionodoxa,
Colchicum,
Echinacea,
Muscari,
Narcissus, and a few that I've forgotten. Most of the visits are at night, though they can sometimes be found in large flowers during the day, hiding until sundown.
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| Dermaptera on Narcissus |
I often encountered pincher bugs in the Narcissus, sometimes even during the day as the large coronas protected them from whatever perceived threats come their way. This one was observed eating the stigma, perhaps with a garnish of pollen.
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| Dermaptera (and a caterpillar) on Muscari |
In a scene like this, I only see one herbivorous insect. It is hard to deny the assumption that pincher bugs feed on nectar when they are seen exhibiting this behavior.
Order Hemiptera
The Hemiptera (Greek
hēmi- or half and
pteron or wing, explanation below), or
true bugs, are a large order with over 80,000 taxa worldwide. What makes it a
true bug? The name of the order hints at one of the characteristics, being that the forewings are leathery on the basal half and membranous on the apical portion, thus
half-winged. Beetles (Coleoptera), for comparison, have forewings that are completely hard or leathery. True bugs also have a beak-like structure for piercing and sucking mouthparts to feed. This order contains many familiar insects from "good guys" like assassin bugs (Reduviidae), bigeyed bugs (Geocoridae), minute pirate bugs (Anthocoridae), and damsel bugs (Nabidae). Less pleasant members of the order include aphids (Aphididae), scale insects (Coccoidea), kissing bugs (Triatominae), and bed bugs (Cimicidae).
Family Rhopalidae
The family of
scentless plant bugs, surprisingly, feed on plants (or sometimes trees, depending on the species). Many eat the seeds, while others eat the plants themselves, though most are believed to be relatively benign.
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| Boisea rubrolineata mating on Cornus (March) |
Like beetles, these two lovebirds decided to meet at a romantic location to do their thing. The Western Boxelder bug feeds primarily on trees (mostly Acer, Koelreuteria, and Sapindus), and they will sometimes form large aggregations, but they aren't considered to be agricultural pests. They occasionally make their way into houses in Autumn and Winter, though they are completely harmless.
Family Miridae
The largest family in the suborder Heteroptera are the plant bugs. They are known as such because most are plant feeders (flowers or other plant parts), or live on plants and are predatory. Due to the large size of this group, they are very difficult to identify, even by the experts. Adding to the confusion, new species are being described continuously and there are likely to be taxonomic changes with so many new introductions as is seen in the plant world.
In general, some are considered minor agricultural pests while others, particularly the predatory species, are beneficial since they actively hunt mites, scale, and whitefly.
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| Family Miridae on Leucanthemum |
In my observations, plant bugs are generally benign creatures that are common sights in many flowers in Spring. They appear to feed primarily on nectar, as seen in this photo where two are seen with their heads in the open florets of this Shasta daisy. The drawback, and telltale sign of their presence, is the spots left on the petals which is their excrement. They are seen in a wide range of floral forms, including Convolvulus, Crocosmia, Echinacea, Narcissus, and others. Some may be attractive for shelter, while others for food. It is also quite possible that, like beetles, they are seeking mates. I do not fret about the discoloration of the flowers, it seems they also must be a food source for something else which certainly must have beneficial consequences.
Family Pentatomidae
This family is most infamous for the stink bugs, but it also includes insects known as shield bugs (a term also used to describe members of the family Acanthosomatidae which have a similar shape). Most species are omnivorous, though the majority of their diet seems to be plant derived. Some are predatory and considered beneficial. Herbivorous species use their piercing sucking mouthparts to feed on plant juices. Predatory species seek out caterpillars and other insects (some of them pests) and use the same piercing mouthparts to suck out the preys juices. No wonder insects are the inspiration behind so many horror film antagonists!
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| Chinavia hilaris on Echinacea |
The genera Chinavia and Nezara are exceedingly difficult to tell apart without highly detailed observation. The two can best be told apart by the absence or presence of black spots on the scutellum (a shield-like structure on their back), as well as a few other characteristics.
Chinavia hilaris is probably the most commonly encountered stink bug in North America. They feed on a huge array of plants, including seeds and fruit, and I would also say that they feed on nectar if it is within reach. I have seen similar species in the flowers of Brodiaea elegans, though the form of the flowers suggest it could have been for shelter as well as a food source.
Order Araneae
Though spiders do not contribute to pollination (or if they do, it is a very minor contribution), though they are by definition floral visitors. They are intimately connected with other insects considered to be true pollinators, and it should be obvious that it is because pollinators and other floral visitors are they prey of flower-visiting spiders. Many of the smaller spiders eat dipterans (flies) and smaller hymenopterans (wasps and bees) while only the larger spiders can successfully capture honey- and bumblebees. Bees seem aware of the spiders presence. I have on occasion watched a honeybee visit every flower around a flower with a spider on it, suggesting that it recognized the threat. Spiders are neat, here are some of the ones I've seen this year:
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| Mecaphesa on Narcissus with Diabrotica undecimpunctata |
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| Mecaphesa on Eschscholzia with a snack (a dead bee) |
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| Captured honeybee on Helianthus |
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| Mecaphesa on Coreopsis |
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| Mecaphesa on Calendula |
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| Araneus (an Orb weaver) |
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| Araneus gemmoides feeding on a honeybee beside Gladiolus |
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| Araneus gemmoides, builds large webs near flowers. |
Have a happy new year!
