Wednesday, February 18, 2015

Aquatic Arthropods in Arizona

Of course, arid Arizona does not seem to be the very best place to look for aquatic life in any form. But we do have a few riparian areas left, some permanent creeks and cienegas, some artificial lakes, artesian ponds, rivers that carry mostly treated waste-water and of course many temporarily flooded areas during a good monsoon season. But where there is water even temporarily, there are always many interesting creatures.

Laccophilus pictus coccinelloides, Sabino Creek, Pima Co, AZ  4-4-2012
Predaceous Diving Beetles (Dytiscidae) were always among my favorite aquatic insects. As a kid in Germany, I used to raise the huge, fiercely predatory larvae of Dytiscus marginalis, one of our largest beetles. But here in AZ I came to appreciate also the beauty of some of the smallest members of this family. Although so prettily patterned, these 4 mm long, fast swimmers are nearly invisible in the tannin-colored water and against the mica glittering sand of Sabino Creek.
 Note the air bubble that is held under the elytra. When the beetle has used up oxygen from the original air, fresh oxygen diffuses from the water into the bubble. It's a physical gill. From time to time fresh air needs to be collected at the surface because the bubble constantly looses nitrogen to the water, which cannot be recovered, so it keeps shrinking. The beetle does not need the nitrogen per se, but it needs to keep up the volume of the bubble to allow for the exchange of O2 and CO2 with the water. So occasionally, it comes to the surface for refills.

Thermonectus marmoratus, Sunburst Beetle
 Here is another beauty, the Sunburst Beetle. It's larger than a penny and catches the sunlight very nicely when it swims in flat water, propelled by strokes of its modified hindlegs.  

Agabus disintegratus, adult and pupa
Most Water beetles like Hydrophilidae and Dytiscidae lay their eggs under water, their larvae are aquatic, but to pupate, they have to come on land. I collected pupae under drift wood at Watson Lake in Prescott and let them hatch.

Large whirligig beetle, Dineutus sublineatus
Gyrinidae are primarily surface swimmers. They often form large aggregations and when disturbed swim in erratic circles (name!) . they have horizontally divided eyes and corresponding brain areas are devoted to seeing above and below the water surface respectively.  

Many true bugs lead aquatic lives, and all states of their life-cycle are water-bound, even though the adults of most species are good fliers. All I can think of a predatory and administer venom and digestive juices through their pointed 'beaks', some have raptorial arms, most have legs that are adapted to swimming and diving.

Graptocorixa (Water Boatman) Nymph
Water boatmen were in the news some time ago. A species in Great Britain was found to be the loudest animal on the planet, relative to its body size. It can create mating calls as loud as 99.2 decibels. The male water boatman produces this noise by rubbing his penis (or “genitalia appendage”) against the ridged surface of his abdomen.

Gerridae, Water Striders
Water Striders, Gerridae skate, using the surface tension of the water as their only support. They are predators and use their tactile sense to locate drowning, struggling insects that cause characteristic wave patterns. Getting close to the source, they switch to chemical prey recognition. A long time study subject of sensory and electro physiologists.

Water Scorpion Ranatra quadridentata, Madera Canyon, Sta Cruz Co, AZ
 This photo, borrowed from Historic Rivers Chapter, shows the bug breathing through a snorkel  at its hind-end. So thisis NOT  a stinger! Instead the bug catches prey with its raptorial arms and injects venom and digestive juices through its 'beak'

Larvae of Archilestes grandis (Great Spreadwing), Libellula sp. (probable Flame Skimmer), and Paltothemis lineatipes (Red Rock Skimmer) photo Bob Barber
 While beetles and true bugs are good fliers and can easily find new ponds and meet mates during their nightly excursions they spend most of their adult live ponds and streams.
Other insects that spread more delicate wings once they have outgrown their aquatic larval phase, do not return to the water as adults, except to deposit their eggs.
This great photo of Odonata (Dragonflies and Damselflies) was taken in New Mexico, but all three species can be found in Arizona as well.

Camelobaetidius larva, Sycamore Canyon, Santa Cruz County, Arizona, USA,
March, 13 2012
 Mayflies (Ephemeroptera) spend the longer part of their lives as aquatic larvae. Note the external gills along the abdomen. Mayflies are famous for the mass emergence of the short-lived adults. Unlike most insects, Mayflies go through a winged subadult state that is followed by one final molt to the imago.

Petrophila jaliscalis, Santa Cruz River, Between Wheeler Taft Library and Ina Bridge, 11-24-2014
Even some Lepidoptera have aquatic larvae:  During the day these little crambid moths can be found sleeping in the vegetation close to creeks and streams. They are night active and come to lights in late summer to fall..
Adult females enter the water to oviposit, carrying a plastron-like layer of air as a source of oxygen
The larvae are aquatic, living within a silken web in fast-flowing streams;
they scrape diatoms and other algae from rocks in streams.

Trichoptera or Caddisflies,, those hairy cousins of the scaly Lepidoptera, are obligatory aquatic breeders. Their larvae build tubes out of detritus and anker themselves on the bottom of slow moving creeks.

Corydalus texanus (Dobsonfly), Clear Creek, Yavapai Co, AZ
This is a female Dobson Fly, about the size of a wooden cloth pin. The males have amazingly long mandibles. Order Megaloptera: The female lays thousands of eggs in a single mass, placing them on vegetation overhanging water. Megaloptera undergo the most rudimentary form of complete metamorphosis among the insects. There are fewer differences between the larval and adult forms of Megaloptera than in any other order of holometabolous insects,  The aquatic larvae are carnivorous, possessing strong jaws that they use to capture other aquatic insects. They have large heads and elongated bodies. The abdomen bears a number of fine tactile filaments, which, in some species, may include gills. The final segment of the abdomen bears either a pair of prolegs, or a single, tail-like appendage. The larvae grow slowly, taking several years to reach the last larval stage. When they reach maturity, the larvae crawl out onto land to pupate in damp soil or under logs. The pupa is fully motile, with large mandibles that it can use to defend itself against predators. The short-lived adults emerge from the pupa to mate and oviposit - many species never feed as adults, living only a few days or hours.

These are just a few examples of the rich diversity that can be found even in Arizona's creeks and ponds. More than any other habitat, these ecosystems are delicate and threatened by pollution, grazing, mining and continuous droughts. 

Wednesday, February 11, 2015

A new True Bug species for our back yard

Leptoglossus brevirostris
 Well, not really new. Leptoglossus brevirostris was described by Barber in 1918. But new to me, and there was only one BugGuide entry so far, and that one was from Texas.

Yesterday I walked around with camera and Frodo to shoot some backyard birds (I finally want to put together a complete photo documentation for our backyard). I found that the desert mistletoe Phoradendron californicum - Mesquite Mistletoe is still blooming, attracting bees, flies and butterflies, but it also already offers enough berries for a number of birds to hang around.
There was also a true bug, a Leptoglossus sp. As 'true bugs' is this weeks theme for our Facebook group 'SW US Arthropods' I spent time photographing it from different angles, took dorsal shots and feeding portraits .... and then let it fly off into the clear blue Arizona sky. I thought I knew the species.

Notice the relatively short rostrum (not the thin filament, the thick kneed beak that just touches the berry)
 At home, enlarging the photos, I realized that I did NOT know the species. I should have collected it.
Recorde from AZ are Leptoglossus brevirostris Barber, 1918
Leptoglossus clypealis Heidemann, 1910

Leptoglossus occidentalis Heidemann, 1910
Leptoglossus oppositus (Say, 1832)
Leptoglossus zonatus (Dallas, 1852)

It did not have even a trace of the two yellow pronotal dots that characterize L. zonatus and that it did not look like L.clypealis, L. oppositus, or L. ocidentalis. There was a close likeness in a photo on bugguide from Texas, but the poster had also identified hers by excluding other possibles. L. brevirostris?

So I e-mailed a photo to coreid expert Harry Brailovsky in Mexico City and also posted it on my personal Facebook page.

This morning I had a Facebook message from Laurence Livermore from the Natural History Museum in London with a specimen photo of L. brevirostris from their collection and an email from Harry - 
Dear Margaret
Good morning from Mexico City.
Close or Leptoglossus brevirostris Barber.  Check if the rostrum is short not extending beyond posterior border of metasternum or anterior third of third abdominal segment (First).
  (my comment: this is visible in the feeding position in the image above)
Harry Brailovsky
Instituto de Biologia,UNAM.
Departamento de Zoologia

So both confirmed that it is Leptoglossus brevirostris. My photo will now be added to the NHM's Coreoidea Species File profile. And of course it also goes into my own personal coreid collection on flickr.  Isn't the internet great?    
Another member of our Facebook group,  GY Zhang, found an interesting paper that deals with the insect fauna on mesquite mistletoe in Texas. It describes our Leptoglossus brevirostrum as host-restricted to this hemiparasitic plant. I knew that several coreids are very faithful to their cactus hosts, so it should not be too surprising that the mistletoe feeder also sticks to this one food source. I'm going to search  tomorrow - I should be able to collect a few specimens after all.

Sunday, February 8, 2015

Batesian and Muellerian Mimicry

Some defenseless arthropods that would make great prey have evolved to resemble other species that are toxic, bad tasting or heavily armed. One precondition must be that the models are not just foul tasting or aggressive, but memorably so: So the mimicked models are announcing their in-edibility with warning colors and patterns (aposematic) and the imitators share in the protection. This is the Batesian mimicry that is often explained using toxic Monarch Butterflies and their harmless look-alikes, the Viceroys as an example. Also similar looking is the Queen Butterfly. Queen and Monarch caterpillars both grow up incorporating toxins from their mutual host, the milkweed plant. In the case of Monarchs and Queens the warning function of colors and patterns is enhanced because they are so similar. A predator who has learned to avoid one will also leave the other one alone. Strength that grows with numbers. This kind of mimicry is called Muellerian.

                     Vespula pensylvanica, Western Yellow Jacket (social), Ancistrocerus tuberculocephalus (solitary), Mischocyttarus navajo (social), Polistes comanchus (social)
A striking and well known Muellerian mimicry group is that of the yellow/black banded, stinging wasps, who share a pattern of warning colors that stayed evolutionary stable even as wasps spread over nearly all continents and formed many different species, genera and tribes. (I am assuming here that this phenotype relies on an ancient gene (group of ). Did the pattern evolve before social hives appeared? The threat of the social group that attacks  together certainly gave the warning pattern its power. Solitary wasps that share it are profiting from the fierceness of their social sisters.

Climaciella brunnea (Wasp Mantidfly), and Polistes comanchus
Batesian mimicry:
Social wasps are probably among the most aggressive defenders of their hive area, so they have many very close mimics. Previously I showed an examples for Muellerian mimicry. Here are some of many examples of Batesian imitators: The Wasp Mantisfly (Neuroptera) is shown with one of its models Polistes comanchus. But other individual in the same mantispid species strikingly imitates solid brown and more strongly banded Polistes species.
Add caption
A moth in the family Sesiidae (Clearwing Moths) and a Syrphid Fly. The moth was so convincing that I watched an experienced entomologist hesitate to take it out of his net by hand. The fly goes the extra mile to camouflage a feature that partly gives away the wolf to Red Riding Hood: Grandma, what big eyes you have! (Wasp eyes are much smaller than fly eyes). You may also notice another obvious difference: the wasp has much larger antennae. So several species of syrphids compensate by flying with their front-legs stretched forward like antennae
Also note the locations (on the individual images): all occur together at higher elevations..

Longhorned Beetle Strophiona tigrina
Several Acmaeodera species in the family of the Metallic Wood-boring Beetles 
 Even many beetles are using the 'yellow jacket' color pattern, especially many flower visiting species. But when beetles want to take off, most (like Strophiona tigrina, above) have to open their hard front wings (elytra) to make room for the membranous hind-wings that are used to fly. So there goes the nice imitation of a wasp. Or does it? Most Buprestides in the genus Acmaeodera have nicely banded elytra and they keep them closed during their frequent flights. The side margins of the elytra are bend upwards and the hind-wings can be stretched out from underneath. The beetles fly with closed elytra and the illusion of a wasp stays intact. There is also a group of scarabs that flies like that (Euphoria) and they very much resemble bumblebees or carpenter bees when flying, they even hit the right buzz. Silberglied, R.E. and T. Eisner. 1969. Mimicry of Hymenoptera by beetles with unconventional flight. Science 163:486-488. DOI: 10.1126/science.163.3866.486

Longhorn Beetle Tragidion decipiens, Tarantula Hawk, Hemipepsis ustulata, and Mydas Fly Mydas xanthopterus, Photo Bob Barber
One of the most painful stings according to Justin Schmidt's Pain index is delivered by one of our big, solitary wasps, the Tarantula Hawk (female only) Of course, there are several Muellerian mimicry 'gang members' like painfully biting Robber Flies and other wasps like a big Sphecid species. But there are also harmless mimics like several Cerambycids (Longhorn Beetles) in the genus Tragidion. These beetles also visit some of the places where the big wasps lick up sweet tree juices. After landing, the beetles often keep their elytra open for a while - very unlike other beetles but in striking similarity with the wasp.

Phidippus apacheanus and Dasymutilla sp.
I am not sure whether the connection between Phidippus apacheanus (probably including several other Phidippus species) and the very painfully stinging mutillids, the orange and red species of Dasymutilla should be called Muellerian or Batesian. Are jumping spiders dangerous prey to a bird or lizard? Probably not, so Batesian. Anyway, the spiders and wingless wasp females don't only look alike, they also frequently crawl around together on the branches of Desert Broom. The spiders are hunting for insects that get attracted by the sweet juices and the wasp is a sweets-lover herself.

Dasymutilla male
Dasymutilla males are also often sleeping close by. They sport the same colors as the females and their wings are folded and hardly visible. Like ALL males of stinging Hymenopterans, they are also just sharing the protection that the aposematic coloration of their females provides. In that sense, most brightly colored male wasps and bees are Batesian mimics of their female counterparts, because NO male hymenopteran has a stinger.

Here is a little Coreid (Leaf-footed Bug) nymph in the genus Narnia and her mom. The little ones were all over the juicy fruit of a Barrel Cactus and its extra-floral nectaries while the adult was hiding among the thorns, very much out of reach. Where the little ones just naively taking a risk or were they protected? The barrel cactus fruit and nectaries are often visited (and owned) by the very defensive local fireants Solenopsis xyloni. The bug nymphs resemble the ants in size, color and preferred location. Not so much in shape. But the resemblance really does not have to confuse the human eye as long as it repels a predator

To dispel the idea that only the very painful stingers among hymenoptera can be mimicry models: Here is a peaceful, flightless, dusk-active darkling beetle, Eleodes armatus on the right. A stink beetle, like all of his genus and many in his family). There are 2 huge glands in his abdomen that douse him and the prospective predator's nose with very obnoxious chemicals. To get good coverage, he lift his hind end where the glands open, high into the air and lets gravity do some of the work. The same-sized Cactus Longhorn Beetles here Moneilema appressum is also dark, flightless, and has to move between cacti across the light desert sand at dusk. So it does a stop-and-go walk, just like Eleodes and even lifts its behind when disturbed. The big dark Calosoma species (Ground Beetle, Carabidae) also joins in the behavioral mimicry, but those guys can release a nice stink by themselves ....

Pipvine Swallowtail, Battus philenor 

Red-spotted Purple, Limentis arthemis
In AZ (and elsewhere in the southern US) where riparian areas interface with desert habitats, we find two butterflies that can be easily mixed up: One is the Pipvine Swallowtail whose caterpillar picks up enough toxins from its foodplant, the pipevine, to make not only the caterpillar but also the adult inedible for many predators, the other one is the Red-spotted Purple. Interestingly, that same species, Limentis arthemis, has northern color forms that look quite different. Check them out on bugguide 
So where the model is not around in sufficient numbers, the similarity provided no advantage and did not evolve.

Lycus simulans and  Elytroleptus ignitus
A final twist: Netwing Beetles in the genus Lycus are highly toxic and announce that fact with bright red warning colors. They also often congregate in great numbers to mate and are hard to overlook. Not surprisingly, several species of Lycus are similarly colored and patterned, forming a tight Muellerian mimicry group. There are several moths and  beetles of unrelated families that mimic them as Batesian groupies.
Were there enough mimics to endanger the whole system? Did naive predators get lucky too often so they did not learn to avoid the insects?
Anyway, there is something very interesting going on in SE Arizona: Several species of the Longhorn Beetle genus Elytroleptus usually associate with the toxic Lycids around oak trees (extra floral nectaries) and on flowers. In those mixed groups, many Lycids looked like they had been chewed on. Holes in the elytra, leaking heamolymph ... Normally we think of all Longhorn Beetles as strictly vegetarian. But it turned out that Elytroleptus were chewing on Lycus, and chemical analyses revealed that the Longhorns were actually incorporating (sequestering) the toxins of the Lycids.  A Batesian mimic becoming Muellerian at the cost of its model!

Saturday, February 7, 2015

Spring is coming early to Arizona

This year we finally had winter rains as they used to be: dreary 2 day stretches of cloudy skies, continuous gentle rain and foggy mornings. Mostly this seemed to happen on the weekends of out-door art shows so my tent is now nearly clean and white again.

Frodo, our Coydog, enjoying his backyard
The desert is responding. It looks like one big golf course with soft green turf. But most of the little plants are no grasses. Many are in the Boraginaceae, the borage or forget-me-not family and have tiny white flowers. Not many showy big wildflowers yet.

omessor pergandei (Messor pergandei)
 Curious crop circles appear - at closer investigation they turn out to be old mounds of Veromessor Pergandei Ants, a small Harvester Ant that piles refuse heaps around its entrances. In that thrash pile were obviously left-over seeds but also probably a lot of nitrogen, always a limiting factor in the desert sand.

Microrhopala rubrolineata , Leaf-mining beetle
Scaphytopius sp. Leafhopper
Corythucha sp.  Lace Bug
The perennial Brittle Bushes are showing only the first traces of flower buds, but their foliage is now a beautiful silvery green. Leafmining beetles, Leafhoppers and Lacebugs are getting a head-start.

Scytodes sp.,  Spitting Spider with Roach nymph
Young Salticidae
 Under bark and fallen logs  hidden activity may go on throughout the winter. A Spitting Spider paralized a nymph of a roach, Young Jumping Spiders are leaving the webbing that has protected them as eggs.

Armadillidium vulgare (Woodlouse)?
 Pillbugs are ready to roll. They need the humidity that the rains brought more than other desert creatures: as crustaceans, they take up oxygen through external gills.  Those are protected in a cavity on the underside of the body and need to be kept moist.

Trichoton sordidum
Tenebrionid beetles are much better adapted to the arid climate, they reach their highest diversity in desert areas all over the world, but this species also prefers the cover of bark and mois places when those are available

Scolopocerus uhleri
Some Coreid True Bugs are active throughout the winter in Arizona. Living on barrel cactus, the Narnia mother can rely on the juicy fruit year-round to raise her ant-look-alike offspring.

Narnia sp.

Schistocerca nitens
Some adult Schistocerca nitens Bird Grasshoppers are still hanging on from last year, but the new nymphs are already waiting in the Creosote Bushes. Not sure that's their food plant, though.

Campsomeris sp., Polistes sp., Anthophora sp.
Warmer temperatures and the first flowers on the wolf berry bush brought out some big chunky wasps and bees, and  identification-wise I can't get any further than the genus.

Sara Orange Tip, American Snout, Texas Crescent, Mourning Cloak, Pipevine Swallowtail
 We have butterflies all winter long if we are not hit with a very hard freeze. Also, waves of migrating butterflies can always arrive from even warmer areas of Mexico.  The first Orange Tips that I saw yesterday are definitely heralding the arrival of spring.

Photos taken in our backyard in Picture Rocks, at Sweetwater Wetlands West of Tucson and Sabino Canyon east of Tucson. All Pima County, Arizona