Fire Ants in Arizona: No Reason to Panic

Solenopsis xyloni (Southern Fire Ant)

Two days ago we woke up to Fire Ants marching across the kitchen counter (after hummingbird food had been prepared there the evening before). A thorough scrubbing of all surfaces will convince them to stay outside, I hope. No new arrivals for a couple of days at least.

Polymorph workers: many different sizes

 On the brighter side, these are our little native Solenopsis xyloni (Southern Fire Ant), not the feared introduced Red Fire Ants, S. invicta, that I met in Florida on my last night of gator watching that left me literally scared for life.  

But our little guys can sting too. When they come to my black light at night to tackle any small scarab that falls and lands on its back, they sometimes also get my toes. They seem to always plan their attacks until several are in position ... just like their bigger relatives in Florida. Their stings burn and itch but are really just a minor irritation. In our kitchen they were so docile that I first doubted my identification. No attempts at stinging at all.

Tackling a Minute Black Scavenger fly

But outdoors they are voracious and attack insects much larger than their size and manage to subdue them. So I assume that the crack in the kitchen wall (?) that they must have found is now free and clean of any other bugs. OK. Just stay off my counter and the floor!

Southern Fire Ants in the compost bin

In the backyard, I have noticed a belligerent colony close to the compost bin. We have lots of space, so this is far from the house.

Southern Fire Ant on a barrel cactus fruit

Solenopsis xyloni are also usually found on barrel cacti. To get the photo for this blog I just pulled a fruit from a barrel in the front yard and immediately had a couple of volunteers. I knew this would be the case because I'd seen the ants on barrels even in winter when I was looking for nymphs of leaf-footed bugs that develop on cacti.

 

At this time of the year saguaro cacti drop their fruit. Birds have been feasting on the sweet seed pulp before the fruit falls, but there should still be enough left to make some ants happy. Under a free standing saguaro, I found some of those fresh bright-red stars. There were some very small extremely fast-running ants, a Pheidole species I believe, but no Fire Ants. Do they not like saguaro fruit? Or are their colonies simply too far from this cactus?

At nigh at my black light site: Southern Fire Ants taking apart a scarab beetle and gorging on sweet saguaro pulp

 To test my theory I moved a few of the fruits to my black lighting site because I know that Solenopsis xyloni lives around there. I turned on my lights for some hours after sunset (a gorgeous one with virga, rainbow, red clouds and early moonrise).
 When I returned the Fire Ants had performed to expectations: not only did they overpower a small scarab beetle (Acoma sp.) and were just testing the resilience of a much larger Oxygrylius, they were also all over my saguaro offering.   

I know that the time of day and temperatures also play an important role in an ant's activity, but I did find Solenopsis xyloni active in the afternoon on the barrels but not the saguaro. Since they obviously love the saguaro fruit, I am back to my idea that there simply is no colony close to the free-standing saguaro.  Why?
To the human eye areas around the barrels and the columnar giant looks quite similar. So is it the cacti themselves that make the difference? Their yearly cycles are quite different. The saguaro blooms in April/May, and has fruit in June. As far as I can tell, those are the only times when saguaros have anything to offer to ants.

Barrel Cactus, this year's flowers and buds surrounded by last year's fruit

 By contrast, the  thick-walled fruits of the barrel stay on the plant, often for years, so several 'generations' of fruit are constantly present, arranged in rings around the center that keeps producing new flowers once a year, in July/August. Eventually the fruit are chewed open by rodents and the seeds disappear, many carried away by ants that are collecting the sweet sticky pulp.
  Barrel cacti also offer sweet sap from extra-floral nectaries all year round. It could be that the barrel cacti (via coevolution) are 'making sure' that ants have a reason to hang around. The cacti may be employing armies of little fighters for their protection against other bugs and the distribution of their seeds by offering them sweets. I have seen the ants attack cactus-juice-sucking coreid nymphs in several cases.

A jumping spider killing a coreid nymph on a barrel cactus

It is possible that barrel cacti rely overall more on arthropods as allies than saguaros do. Saguaros have many avian house guests that nest in or on the cactus or feed on nectar and fruit pulp. Many of them are insectivore gleaners like cactus wrens that also peck many insects off their host's thick skin.
Barrels are very vulnerable to rodents so they are tightly covered by a mail of interlocking thorns. This formidable defense may keep many birds from spending too much time on a barrel, and at any rate barrels are not tall enough to provide protective spaces for nests. Ants and spiders however have the ideal size and agility to police that space under thorns and between ribs. 

 Both saguaro and barrel cacti eke out a living in spartan surroundings. There is not much more than sand, widely spaced creosote bushes and cholla cacti. Under these borderline conditions the reliable yearlong provider may win out over the once-in-a-year party host when the opportunistic Fire Ants are choosing a neighborhood to live in.

Pheidole sp. left and Messor pergandei right. Colonies close to the saguaro

 I am not saying that the saguaro neighborhood lacks ants: besides the Pheidole colonies, there is a huge permanent Messor pergandei colony. But those ants have a completely different social, foraging and storage system than the Fire Ants. 

With this blog, I would like to stress that not all ants are alike, every species has its own ecological niche, and not even all Fire Ants are alike. The imported, highly invasive Red Fire Ants are established all the way from Florida into Texas in the east and  in California in the west. But they need more moisture than they would find in southern Arizona and they may be too frost sensitive to live on the Colorado Plateau in the north. So they may never overrun Arizona.

Living with ants (and you will, if you live in Arizona) is easier and far more interesting if you learn about the different types, one species at a time. Theirs is a densely populated and highly socially organized world to discover.

Please do not contact me about methods 'to get rid of ants'. I have no experience in that field and - beyond my own kitchen counter - no interest in gaining any.

Dynastes granti, the largest Arizona beetle

If all gas stations were this clean, I'd have more fun collecting Dynastes granti

The Hercules Beetles are flying! Even though some 'real' entomologists scoff at my appreciation of these big, shiny, horned giants, I am looking forward to their late-monsoon appearance every summer.

Apparently I am not the only one, as this photo of Bill Warner shows. He is one of our leading scarab specialists (photo by Ben Warner).

On my Beetle Safaris with clients, I usually look for Dynastes granti at  artificial light sources with a strong UV component, like those arrays of mercury vapor lights at some gas stations along the Mogollon Rim in central Arizona. The further away from civilization and other lights the better. Most of those locations are well known and draw beetle collectors from all over. Even though the competition is usually good-natured and one is at least rarely alone, it is not always pleasant to spend the night at a gas station in the middle of nowhere. But if the weather is right, a warm night after a storm is ideal, the beetle hunt in those locations is usually rather successful.

Young Ash Trees in a canyon close to Prescott

By far more interesting and esthetically pleasing are the natural gathering places of the big beetles:.   lush stands of ash trees along creeks in little canyons. The beetles love the sap of ash trees that is raising after the monsoon rains in August. To get this treat, male beetles chew through the outer bark into the cambium layer so the sweet sap begins to ooze. They pick young branches of less than 3 inch diameter that are still tender and green. The chew marks have a characteristic shape. Even years later when they are covered by scar tissue they are still easily recognizable. In fact, those left-over scars were all I could find at first. I also discovered that under some ash trees, someone had turned over the soil. Left over beetle wings told the story: Scarabs, not all of them Dynastes, had been attracted by the oozing sap at night and then burrowed into the soil in the morning. Some large mammals like javelinas or skunks had learned to search for snacks in this promising locations.   

Left and middle: fresh bark scrapings, right: old scar all on the same Ash tree

The scarab-tribe of Dynastini is mainly night active. Most species are big and muscular enough to shiver efficiently and warm up to operating temperature even when it's cool outside, and once warm, they are strong fliers. So at night they fly to their ash trees, prepare their sap licking sites, congregate and find mating partners.The males use their horns to grab rivals and toss them off the tree. I assume the winner gets the girl...but I have seen males push females off the food, too, so fermenting tree  juice may be even better than sex.

  I started my search in the early morning because I had been told that the beetles, once they had chewed a sap producing wound into the tree, would hang around during the day, mainly resting in place from their nightly activities. It was at first difficult to spot them because they were all rather high above my head, at about 12 feet. So I was staring up against the sky while at the same time trying to keep my footing on slippery rocks and not to stumble into the creek. Catching them was a whole other problem. The two first ones I spotted took off, buzzing like helicopters, as soon as  my net came close to their branch. In the act of mating, they were obviously alert and warm enough for immediate take-off.  They disappeared high into the blue sky. Night-active scarabs? 

 Something else moved. Disappeared behind the branch. So I scrambled across the creek to check the other side. The right size and color, but - a cicada.

Slowly a search image formed: the beetles are round and shiny like ripe chestnuts, just not brown but greenish like the ash leaves themselves. And unlike chestnuts, they were not going to eventually fall down. I had to make them. So I got a thin stick, long enough to reach the beetles while I was standing on a tall boulder in the creek. I found that single males could be encouraged to walk down from their perches by pushing the end of the stick between their two horns. By backing off, they may have reacted as they would when faced with a powerful wrestling partner of their own kind. So I coaxed several males within range. A single female fell into the creek and I fished her out.
Overall the technique was extremely exhausting but fun.

The result of an over 400 mile round trip

During the following night I collected a few more beetles at a gas station so I went home with an even number of males and females.
The beetles will augment my own breeding stock, and a few are going to other breeders. A Montessori teacher is building a school project around a pair, the insect photographer Alex Surcica ordered some as models, others will go to entomology classes, an insect festival and a museum exhibit. With some luck, they can outlive their wild brethren by any number of months.
It turns out that I did not get quite enough specimens this year.

Eggs and larva of Dynastes granti, pupa of Strategus sp. ( Strategus is another Dynastini, I have no Dynastes pupae yet)

But that's okay. Last year I kept eight females who produced eggs from September until the end of November. The eggs then rested until January when most of them turned into little c-shaped larvae. They began feasting on fermented hard-wood mulch (my own month-long preparation) and grew quickly into very substantial grubs. They are still eating and growing now, a year after the eggs were laid. For Dynastes granti, the cycle from egg, to larvae (3 instars), to pupae, and finally adult beetles can take up to 4 years. At the Arizona Sonoran Desert Museum a batch took only 1 year, but the resulting beetles were tiny and unsatisfying. According to anecdotal evidence, temperatures and the availability of protein in the larval food have an impact on the length of the development time and the size of the adult specimens. But how those factors are correlated is impossible to tell without rigorously controlled experiments.

A male Dynastes granti has 2 horns. One on his forehead, one on the pronotum. By moving his head up and down, he can use the horns like the jaws of a pair of pliers. He can grab another beetle around it's 'waist' and toss him over his shoulder

And I'm really just breeding beetles for fun ... but I can already see that I could be easily tempted to add a couple more species to my beetle breeding room - there is still space on the shelfs....

Cottonwood Stag Beetle, Lucanus mazana, with egg and young larva

By the way, I just discovered that a Lucanus mazana female (our only Arizona stag beetle) laid eggs in her container and the first larvae are hatching ...

When everybody should become night active

On the east side of the Tucson Mountains, Saguaro fruit are ripe and the buffet is open! Photo by Doris Evans

June was always hot and dry in the Sonoran Desert, and climate change is making it noticeably more so. Most plants seem to take a break from blooming and growing, but the desert trees and bushes like Creosote, Palo Verde and Ironwood are all bearing fruit now.

On our side of the Tucsons, the Cactus Wren is determined to be the first in line when the green fruit finally pop open

Our Saguaros are still producing a few late flowers but by now a few fruits are ripe, breaking open to show their bright red insides. The birds that have been visiting the flowers for nectar are back to harvest the seeds in their sticky sweet matrix. All those plants are ready to have their seeds distributed just before the first monsoon rains in July (?)

We are enjoying June as a slow time with neither art shows nor entomological engagements. During the heat of the day we eat lunch and breakfast on the shady patio, but otherwise we hide indoors were cool air is blowing in from the swamp coolers on the roof.
 We take the dogs for walks in the state land close to sunset or sunrise. Twilight brings a pleasant, magical time with long shadows and warm colors. I would love to capture the running dark 'pups' against the light when they are outlined by gold. No such luck yet.

Day-active animals like squirrels, songbirds, kestrels, quail, zebra-tail lizards, tarantula hawks and dragonflies are still out, and of course the crepuscular dawn and dusk critters. Night active Great Horned Owls and tiny bats begin their activity when the sun has just set. Snake encounters are likely, but lately we've seen only their tracks.

This morning I carefully approached on some Lesser Night Hawks that had just landed. If I do not see them in flight first, I can rarely find them as they tuck themselves tightly along a branch that their feathers exactly match to spend the day.

I also love the warm summer nights. I walk around armed with a flashlight hoping to see Kangaroo Rats and night-crawling snakes. Much more regularly I find the miniature version of the K-rat, cute little pocket mice.

They love to chew on succulent agave leafs. When I taught renal physiology at the U of A I always tried to impress the students with the fact that the renal concentration  capacity of these guys is so great that they can live basically without access to free water even if their diet consists of seeds and dry grasses. I guess being able to live that way doesn't mean they would not rather eat juicy stuff.

Eleodes armatus and Moneilema gigas

Last night I was looking for cactus longhorn beetles  on a cholla where they feed and oviposit at night. The flightless beetles are good mimics of the smelly Pinacate Beetle (Eleodes sp,) whom they resemble in size, shape and behavior when they need to cross open ground.

While peering into the cholla  I nearly bumped into a couple of birds asleep in the relative safety of their prickly retreat. A Curve-billed Thrasher moved away from the glare of my light, but a male Gambel's Quail sat there like he was transfixed. Most birds cannot see well at night, so they are very reluctant to give up their perches. I had never been this close to a wild quail before!

Good night!

 

Early June at the Black Light in our Backyard

Berothidae (Beaded Lacewings)  Lomamyia sp.

Hemerobiidae (Brown Lacewings)

Corydiidae (former Polyphagidae)  Arenivaga erratica

Tettigoniinae (Shield-backed Katydids) Eremopedes sp.

Tettigoniidae (Katydids) Insara covilleae (Creosote Bush Katydid)

Gryllidae (True Crickets), Gryllinae (Field Crickets)  Gryllus personatus (Badlands Cricket )

Reduviidae (Assassin Bugs), Triatominae (Kissing Bugs), Triatoma (Bloodsucking Conenoses), Triatoma rubida

Oligotomidae, Oligotoma nigra (Black Webspinner)

Formicidae (Ants)  Camponotus (Carpenter Ants) Camponotus fragilis

Tenebrionidae (Darkling Beetles) » Pimeliinae » Vacronini

Scarabaeidae (Scarab Beetles)  Dynastinae (Rhinoceros Beetles)  Hemiphileurus illatus

Cerambycidae (Long-horned Beetles),  Elaphidiini,  Eustromula validum

Cerambycidae (Long-horned Beetles)  Elaphidiini  Anelaphus subdepressus

Pythidae (Dead Log Beetles)  Trimitomerus riversii

Lycosidae (Wolf Spiders),  Hogna carolinensis (Carolina Wolf Spider)

Theridiidae (Cobweb Spiders), Latrodectus hesperus (Western Black Widow)

Hoffmannius confusus, a relative of the Stripetail

Sonoran Desert Toad, Incilius alvarius, former Bufo alvarius

This blog will be expanded as the month of June progresses. This first entry is from June 3, the temperatures have reached 105 F, no measurable rain for months, some saguaros are still blooming and others show the very first red fruit. 

Searching for scutigeromorph centipedes

Dendrothereua homa (Arizona House Centipede) photo by jan nadeau

Last Thursday I took a German scientist who is working at the Department of Neurophysiology at the U of A on a tour of our canyons to search for scutigeromorph centipedes. They are long-legged, night-active and, as it turned out, elusive. We have an endemic species here Dendrothereua homa (Arizona House Centipede), which I have seen, once, and supposedly also the introduced species Scutigera coleoptrata (House Centipede) that is more common in the eastern US where it lives in human dwellings. Here it would probably be able to live outdoors, maybe in pine forest like in the Mediterranean. But between Florida Canyon, Pima County, and Sycamore Canyon, Santa Cruz County,  all the creek beds with rocks and soil (leaf-litter) loose enough for these guys to maneuver in were so dry that we found very few creatures hiding under rocks and none of the ones we were looking for.
 

Vaejovis spinigerus, Arizona Striped Tail Scorpion

We did find a number of scorpions, though. Mostly Arizona Stripe Tails, but also a few Bark Scorpions and the one below that still awaits identification.

Diplocentrus spitzeri (?)

The toothy chelicera remind me of Dipocentrus spitzeri that Warren Savary once found on our trip to Peck Canyon. That's not far from Sycamore and the habitat seemed similar (I only saw it at night)

Rabidosa santrita with eggs

 Of course we found ant nests,  disturbed a number of spiders that were hiding under rocks, and where it was moister, big groups of Bombardier Beetles were huddled together.

Bombardier Beetle, Brachinus elongatulus and False Bombardier Beetle, Galerita mexicana

Twice I found a much larger Galerita mexicana, a False Bombardier Beetle, among them. I knew that this species may be mimicking those armed-with-explosives guys, but I didn't know that it actually hides among them...Too bad that all those carabids run so fast when uncovered - I didn't get a decent shot at them even though by then I had my camera always ready.

The female Chihuahuan Toad Lubber on the other hand was sitting still for as many photos as we wanted to take. My German companion asked which toad she might be mimicking. But toads here are mostlt night active, the grasshopper is day active.  She does look very similar to a Canyon Tree Frog, but most importantly, they both look like a rock. So I'd say that this is a case of convergent adaptation, not mimicry but simply camouflage.

We had started our trip in Tucson at 6 am because I was afraid that it would get too hot later in the day. The predictions were for temperatures in the triple digits. But all morning long the sky was overcast and grey and it stayed cool. During our short stop at Pena Blanca Lake it actually rained. Unheared of in May! Consequently, I left my camera in the car. Also unheared of. 

Both lacking cameras, we found a great new (to me) reptile under the loose bark of a burned tree: it was 4 to 5 cm long (without tail), shiny-smooth and had cream colored stripes on a dark brown body. The most impressive feature was the strikingly electri-blue tail. And it posed perfectly on the smooth bark of the tree...

It very much resembled the juvenile Wester Skink in my field guide. But that species should be only in the NE corner of the state, and Pena Blanca is as far south as you can get in AZ. We met a couple of herpers later who said that there is an endemic species around Pena Blanca. Not in my field guide, though.

As soon as it got warmer around noon, many Elegant Earless Lizards showed up. His bobbing rhythm is an extremely fast nodding towards the intruder or the object of his desire.

Large Whiptails were foraging. I think this is a Canyon Whiptail still in juvenile colors even though he was at least 7 inches long without the tail.

We met some 'herpers' who had caught a small mud turtle. The reticulation of the face and the little spur under the chin indicate that this is a Sonoran Mud Turtle.

So we saw a lot of interesting things and time flew by in a hurry. We turned hundreds of rocks and found scolopedromorphs and other centipedes, just no scutigeromorphs. This is the first time that I guided an excursion to find a special arthropod and failed. I did know that they had not been seen here in the arid pre-summer, but the opinion was that these centipedes cannot dig deeply into the soil because of their long fragile appendices and that they cannot stay inactive too long because they have to satisfy their need for water by either feeding on prey or drinking. So can they not aestivate? To survive here in Arizona they may have to.
If any of my readers find any or know about either the local Dendrothereua homa (Arizona House Centipede) or the introduced species Scutigera coleoptrata (House Centipede) - they are still needed! Please contact me at mbrummermann@comcast.net