Sunday, March 31, 2013

Pollination by Seedbug?

Last night I found a Large Milkweed Bug, (Oncopeltus fasciatus), asleep on the underside of a Brittlebush (Encelia farinosa) flower. Nothing special in itself. There were beetles, spiders, flies, male sand wasps, aphids....all tucked under the umbrellas of those little sunflower cousins.

But I noticed that underside, legs and even antennae of the seedbug were covered in yellow pollen. Did the sticky stuff just get on him because of his choice of bed? True bugs (Heteroptera), with few exceptions, are not considered good pollinators even if they hang out on flowers. They are usually there to hunt if they are predators, or suck juices from the plant tissue.  So the invitation to pollinate, extended by the plant in form of nectar and extra pollen to draw insects to its reproductive organs, is usually lost on true bugs. Or so I thought.

This morning the brightly colored seedbug was still around, this time on the flower surface. A brittlebush flower, like a sunflower, is really an inflorescence that is composed of hundreds of single florets, each with a complete set of stamens, pistil and nectaries surrounded by the fused, tubular corolla. So what looks like a simple, easily accessible disk flower can really only be exploited by insects with adequate elongate mouth parts. Of course, bugs do have a long thin proboscis.

 I watched the Large Milkweed Bug walk from floret to floret, sticking this proboscis into everyone, just like a bee of butterfly would. I even took a video. The bug was clearly going for the nectar deep in the florets and while doing so got powdered all over with pollen. I watched him visit several compound florescences. Does that make him an effective pollinator? Probably about as much as any butterfly, if not quite as good as a hairy, dedicated bee.
It's nice to see something unexpected right in my backyard in the early morning. I love my patch of brittlebush.

Saturday, March 30, 2013

Early Cactus bloom in our Backyard

Opuntia Hybrid?
Opuntia macrocentra, Longthorn Prickly Pear, Texas
Echinocereus pentalophus, Ladyfinger Cactus
Claret Cup Hedgehog


Strawberry Hedgehog, Arizona

Cane Cholla, Arizona

Harisia sp.
Chamacereus silvestrii from Argentinia

Beavertail Opuntia, Arizona

From our cactus garden. Most are part of the Arizona landscape and grow somewhere on the grounds without much more water than nature provides. Some are from Bach's Cactus Nursery and grow better in pots with just a little more care, but all love the Arizona sunshine.

Wednesday, March 27, 2013

Desert Bees

We have a collection of early spring bloomers in our backyard, a mix of imported and native species. Right now, there are several penstemon species, aloes, creosote and brittle bush in full bloom.

Parry's Penstemon is a native species. It can be found in many sandy washes of the Tucson Mountains and beyond. In our garden it is blooming in direct vicinity of several showy Aloe species.

The imported Aloes attract the equally imported Honey Bees, and birds who are not very fussy when it comes to sweet juices.

 Hummingbirds, Gila Woodpeckers and Orioles are frequent visitors. But the native Parry's Penstemon is visited by local specialists.

Habropoda  and Anthophora Bees hover from flower to flower, land, and are gone again. Every flower seems to yield  only a very small amount of nectar. This makes life difficult for macro-photographers, but even more so for the bees.

This becomes obvious when the sun disappears shortly behind a cloud resulting in an immediate drop in temperature. Some bees keep going and going. But others soon drop out of the race for nectar. They clamp their mandibles on a leaf or a stem, tuck their legs and rest motionlessly. I can see that they do not carry any loads of pollen, and when one finally starts moving again I see a flash of white from the face: the bees that take brakes seem to be all males. They may stop flying when the temperature drops and they would have to spend extra energy on heat production to keep their flight muscles operative. For males this expenditure may not be worth it. The resting individuals also looked old and ragged. Maybe they have done their duty.

The pollen loaded females who are provisioning their nests seem to have reasons to invest more energy and keep flying, at least at our only slightly sub-optimal temperatures. 
 Habropoda  and Anthophora are Anthophorine Bees with very long togues (0.4 to 0.8 inches) that enable them to pollinate deep flowers (O’Toole & Raw 1999). Adapted to both temperate and tropical climates Anthophorines are wide-spread, but in the US most abundant in the West and Southwest. They are called mining bees because they are solitary ground nesters whose females dig tunnels in the soil to accommodate a series of brood cells. The cells are lined with an oily substance for protection against moisture and fungal infections.

While watching the bees for hours on several days I saw very few honey bees visit the Penstemon, but quickly return to the aloes. The native Habropoda  and Anthophora Bees completely ignored the aloes and concentrated on just one species of penstemon and the surrounding creosote bushes. Every evening, when it's too cool for most bees, a big female Carpenter Bee also harvests pollen from the creosotes. I will have to use a flash to get her photo.

See also:
The Great Sunflower Project, Anthophora – mining bees (family Apidae)
by Lisa Schonberg and Mace Vaughan (Xerces Society) and Gretchen LeBuhn (SFSU)

Friday, March 15, 2013

Adaptable Immigrants

Parry's Penstemon on the left, pink flowers
After an unusually cold January when temperatures dipped to -8C for several nights, in mid-February our Parry's Penstemon was already pushing up its new flower spikes. They seemed to grow fast enough to watch them get taller.

5th instar caterpillar, leaf-cradle pulled apart
 But two of the stems were bent and crippled.  Each one hosted a single leaf-rolling caterpillar in its tip. The caterpillar had pulled the young leaves into a cluster and thus interrupted the growth spurt, causing bending and twisting of the stem. As the caterpillars seemed close to their presumed final size, I collected the two culprits with enough plant material to finish their development. The rest of the penstemons survived a rare snow fall, and  now they are blooming beautifully.

On February 28th one of the caterpillars had pupated in a loose mesh of silk on the rim of the container and I thought the other one might have been killed by the fungus that eventually enveloped the collected plant tissue. I was wrong, I found another adult moth on the ceiling of my studio today.

Antigastra catalaunalis
 On the evening of March 13, a fresh new crambid moth fluttered out of the container. Avoiding the only light in the room, it spiraled right up to the ceiling, causing me to run to the garage for a step ladder and to take this overhead shot. While it's not the straight on dorsal photo that I was aiming for, it shows the flange on the front tibia that seems characteristic for the species. An elegant little moth and a mystery for a while - I had it on BugGuide and sent it to some friends who work with moths, but got no results. Until I posted it directly to Maury Heiman's fb page. Thanks again, Maury!

His Id lead to more information: The little moth in the family Crambidae (Crambid Snout Moths) » Subfamily Pyraustinae » Tribe Spilomelini » Genus Antigastra is called Antigastra catalaunalis (Sesame Leafroller Moth - Hodges#5181). It is an introduced species that is now widespread in tropical and subtropical regions of the world. In the US it is found from Southern Arizona to the eastern Mojave Desert and north to the northern areas of Utah.

Indian Insect Life: a Manual of the Insects of the Plains by Harold Maxwell-Lefroy.
Older descriptions which I found on Wikipedia call it an Indian Moth, but mention its migratory habits and a rather wide variety of host plants: The larvae feed on Antirrhinum, Linaria vulgaris, Sesame and Scrophulariaceae and Pedaliaceae species.

A research paper from India studying the moth's life cycle on Sesame as the host plant finds that warm temperatures and low rainfall and humidity favor population explosions of the moth. Those are conditions  that it will find here in Arizona.
In October of 2012, Carl Olson (duh, I could have just asked my friend and collegue right away!) found that reports were flooding in about unusual damage to landscape plants, such as Tecoma stans (yellow bells) and Tecoma alata (orange jubilee). Dark larval droppings, webbing and a loss of green leaf tissue were the obvious signs and symptoms of activity by the leaf-tier caterpillar, Antigastra catalaunalis. He suggested that since the caterpillars were tightly rolled up in leaves they were protected from most predators and contact pesticides but might be controlled using high doses of products based on Bacillus thuringiensis.

Since to our knowledge the moth hasn't been in Arizona for long, not much is known about its life cycle here, but I can now say that there is at least an early spring (Penstemon) and a summer (Tecoma) generation. These plants in the families Scrophulariaceae and Bigoniaceae and common in the wild as well as in landscaping around Pima ad Maricopa County. The landscaping plants, being grown in high concentrations and often under sub-optimal conditions, will probably suffer more than their wild relatives. I imagine that the population of the species might shoot up to an initial peak as many introduced species do, but then decline gain as diseases and predator populations catch up.  
In 2012 Carl Olson speculated that these immigrants may not be able to survive our occasional cold winters (the winter of 2011/12 had been very mild). But  my early collection date, right after the very heavy freeze of 2013 (Jan 13 to 16), indicates that the moth (its eggs?) might be rather freeze tolerant.

Penstemon parryi and Pipevine Swallowtail (Watercolor by M.Brummermann)

Wednesday, March 6, 2013

Mating season for backyard raptors

Prairie Falcon photo by Ned Harris
This morning we watched an aerial ballet high in the sky above our backyard. A falcon was soaring, but with his feet hanging down, then banking, spreading his tail feathers, diving a little, catching himself again...I first thought that it was a Kestrel hunting insects. But when Randy brought my binoculars I recognized it as a bigger bird, a Prairie Falcon. He kept circling, diving and banking for more than 5 minutes and was finally joined by his partner. They circled together and then sped up towards Panther Peak.

 We don't seem to have an American Kestrel pair in our saguaro this year, but we sometimes hear  mating calls and see the male fly over. They are probably nesting in the State Land to the north.

Our Dark Female, the Red-tailed Hawk, has flown over a couple of time too, and now she is settling in the Saguaro nest that she used two years ago, she seems to alternate nests regularly. Both sites are along a wash in the state land, only about 300 feet apart.

Great Horned Owls are hooting at night from the Twin Peak on the east side of our land. We found a dead one this winter, but there must be a resident pair again.
 We also found a dead adult Harris Hawk. We have no power lines here that could electrocute them. I hope they aren't dying from an environmental poison. High in the food chain, raptors are always at risk.   

The Cooper's Hawks are also getting territorial. For the first time ever I saw the female go very aggressively after a juvenile Red-tail that likes to hang around.
We also have a ghost, a silver grey male Northern Harrier, but he only visits regularly every winter and then disappears for the breeding season.
With all those raptors getting ready to breed, we are hoping for enough rain to keep the land green and productive. But does the next storm have to hit right during my next art show in Dove Mountain? On my birthday???

Friday, March 1, 2013

It may be all about the temperature

When I turn on my black lights during a cool winter night I always hope to find something special. While there are bug collectors beating on every bush and mercury vapor lamps glowing in every clearing in July and August in Arizona, not many out-of-state entomologists come out here in winter and even we locals prefer a warm fire place to a cool bug light.

Last night I found a few geometrid moths, some spiders, and a lonely click beetle. Two leggy insects looked like they might be a type of Thread-legged Bug. But the antennae seemed wrong and the abdomen too heavy.  At closer investigation they clearly had the head of a crane fly, but no wings!
When I enlarged my photos I found that they did have tiny, obviously dysfunctional wings.
The other obvious difference to other crane flies was the body shape: The thorax was hardly wider than the elongate abdomen. 'Normal 'Crane Flies that have a pair of long narrow wings support those with a bulging, muscular thorax. No functional wings, no big flight muscles...

Dactylolabis (Eudactylolabis) vestigipennis
 The fly I found seems to be Dactylolabis (Eudactylolabis) vestigipennis. Thanks to John Carr on Bugguide for the identification. Dactylolabis is a genus of crane fly in the family Limoniidae. It is placed in its own subfamily, Dactylolabinae. Most species are winged.
The type specimen of D. vestigipennis, curated at the Smithonian was collected in the Tucson Mountains, and I found mine in the bajada of those mountains. Others were reported from the Mojave Desert further west and all around this time of the year.
 This means that the temperatures that these nocturnal (?) crane flies are likely to experience during their adult lives are very low.  In February the night temps in the Desert hover close to the freezing point. Yesterday I measured 36 F.

Flying is not only a high energy sport in itself, its apparatus also requires a certain minimum temperature to function. Many good fliers among insects, like bumblebees, sphingid moths and big beetles are able to generate the necessary heat metabolically. They shiver just like birds and mammals.  So at times they are endotherm  like those higher vertebrates.  But while most birds and mammals maintain high body temperatures almost constantly, these insects turn on the heat production when needed, that is when they need to fly at low ambient temperatures.   
The obvious reason is the cost of that heat production as the energy consumption of those shivering muscles is high. When bumblebees in cold climates live around flowers that provide only small amounts of  nectar (asteraceae) they don't fly on cloudy days and remain cold-blooded, while those with access to high-yeald flowers (Fire Weed) will increase their body temperature and fly on rainy days. (Bumblebee Economics, B. Heinrich, 1979, Harvard University Press)

The small moths in the family Geometridae that are coming to the lights right now are unable to increase their metabolic rate for heat production. They don't have the energy to spare, because they don't feed as adults. Their mouth parts and digestive system are reduced and non-functional. Investment in these structures would be wasted because they fly mainly in winter when there are hardly any nectar-sources available, even here in Arizona. So they rely on the resources that they amassed during their larval state. Still, the light, slender males are able to fly in cold temperatures due to their large wing size and special adaptations in their enzymatic make-up. Interestingly, in many species the heavier females of these winter moths are wingless and earth-bound.

Dactylolabis (Eudactylolabis) vestigipennis

Surprisingly little is known about crane flies, considering that some winged species are inch-long and in-your-face-obnoctious if you sit outdoors by candle light on warm summer evenings. The larvae usually feed on decaying plant tissue; some species are carnivorous, and others damage the roots of cereal and grass crops. Most are found in semi-aquatic or at least moist habitats. The feeding habits of the short lived adults are not well described. Some possess a long slender proboscis and feed on plant nectar. Not surprisingly, I couldn't find any info on the life cycle of this tiny (11mm) inconspicous species.

The tip of the abdomen

the narrow thorax with reduced wings

the head
But I think I can guess why these flightless guys should turn up during cold winter nights. Even under the microscope I cannot find a proboscis, so they may not feed at all. The two that I found may be females - the males may be able to fly? I will place them into a flight cage tonight to see if they attract the opposite sex. Anyway, I assume that the reduction of wings in this species is an adaptation to a biological niche where the ability to fly would be very costly because of the low ambient temperatures that these insects live in. 

Winter and night activity opens an ecological niche to insects that have little other protection against predators. They live their adult lives in the cold, maybe without food, but also out of reach of day-active birds, summer-active bats, and most predatious insects so they can focus on their only purpose: finding a mate to propagate their genes.