Wednesday, October 27, 2010

Lubbers, our largest Grasshoppers

Even though grasshoppers and their growing nymphs can be found in Arizona at all times of the year, they really seem to dominate our insect fauna in late summer and autumn. Our local species hardly ever develop population densities that would induce them to turn into wandering bands of Locusts, but when you walk through grass land or brush a few of them seem to jump up under every step.

      Chihuahua Lubber                                    Horse Lubber                                    Plains Lubber
Phrynotettix tshivavensis                       Taeniopoda eques                             Brachystola magma

Because of their size, the heavy-built Lubbers or Romaleidae are especially conspicuous (Two immovable spines on the hind tibia separate them from Acrididae who have only one spine, but mostly they can be recognized by their large size and lumbering gate).
 So far, I have found the three species shown above in southeast Arizona. I am still hoping to find the Furnace Heat Lubber, Tytthotyle maculata, and the rare Spanistic Desert Grasshopper, Spaniacris deserticola, both in western Arizona.

The strange looking  Chihuahua Lubber is the rarest of the species that I found. It occurs in early summer in rocky or gravelly arid areas from the lower desert elevations up to the oak and juniper belt of the mountains.
 Chihuahua Lubber, Phrynotettix tshivavensis

Their compact shape, brownish color, and warty surface hide the flightless lubbers very well in that environment. It took me years to find my first one in Brown Canyon in the Baboquivari Mountains, but then, after having established a search image, I also found them in other places like Canelo Pass south of Sonoita and Florida Canyon in the Santa Ritas. Our Chihuahua Lubber is considered a distinctly different species from the Robust Toad Lubber, Phrynotettix robustus that is found in Texas.


The Plains Lubber has a wide, but patchy distribution. This year they seemed to be a banner year in southern Arizona, with big males basking in the sunshine wherever sunflowers or rabbit brush lined the road sides and even mated pairs slowly crossing the roads. 

 Plains Lubber Brachystola magma

Eggs are laid in the ground in pods of about 20. In a the USDA study the eggs needed two years of incubation and over-wintering before hatching. Field observations of population peaks in alternate years support the hypothesis of a two-year life cycle. 


 The nymphs hatch wingless and undergo five molts before they mature. The adults have only very small non-functional wings and their only means of dispersal is their lumbering walk and slow jumps. They feed voraciously on many different plants but seem to prefer the sunflower family. Only rarely do they venture into cotton fields and do some damage to the crops. Mainly phytopagous, they supplement their diet by scavenging and have been observed to kill  and eat smaller grasshoppers.



The Horse Lubber Taeniopoda eques is locally known as Mexican General. That's because of his bold aposematic coloration, over 3 in length and stately movements. In some years in October, when the lubbers cross the roads to Madera Canyon and Mount Hopkins by the hundreds they look like an army on the march.
 Horse Lubber Taeniopoda eques female
This female is roosting high in a mesquite tree before night fall. Most likely, this will allow her to catch the early sun shine to warm up and get active quickly in the cool desert morning. It's October!

Although many of the males have functional wings, they rarely fly. Instead, they use their wings in a defensive display when they are threatened. The flashing of the red hind wings is accompanied by clicks from the front wings and hissing. I addition, they may exude foul smelling froth from their thoracic spiracles (breathing openings).

Defensive pose Photo Katrina Weber

Judging from the numbers of Horse Lubbers that walk around openly and unencumbered by birds or other predators,  the strategy is working. However, many get run over by even the most respectful drivers. Any roadkill is immediately cannibalized by the survivors, often resulting in another series of traffic calamities.  Otherwise, they feed on the foliage of Mesquite and other brush and broad-leaf  weeds. 


Early instar nymphs tend to stay together in groups. I have found them in early to mid August and the adults as late as the end of October.












Friday, October 15, 2010

Western Diamondbacks' mating attempt in fall

October 16, 2010
In front of my studio window, we have a little 'house' that protects one of our quail blocks from being carried off by coyotes or dogs - havelinas can't get through the backyard fence. This morning there were coils moving inside.
At first, we couldn't quite make heads or tails of it - there were too many loops. Then we saw the head tapping the back in an unusual motion, tenderly?.
Ok, two tails, and intertwined in a suggestive position. They mate in October? Normal mating season is in spring, I saw them in April. Fall matings do occur, though. In that case, the sperm will be retained viable by the female until spring, resulting in birth in next years warmer season. Interesting, but right under my window? in the dog run? Sorry, but we asked them to move.
Free transport provided - into the State Land next door. Yes, they can come back, but if they don't, others will. There's no vacuum in nature.

Pretty angry at first. Who wouldn't be. But we picked a nice place for theme in a dry wash with lots of rodent holes.


They took off together. I hope we didn't spoil their mood.

Tuesday, October 12, 2010

The Euphoria species of Arizona, USA


Overall, in 2010 the numbers of insects in Arizona seemed rather low compared to for example 2007-2008. The extremely dry summer of 2009 and a general increase in temperatures may be the reasons. Small, short-lived and heterotherm, insects are likely to be sensitive to climatic changes. Many species may also reach the limits of their tolerance in hot and arid Arizona. If it gets any hotter and drier here, they may not survive. But so far we are still hoping that this was a temporary decline in numbers and that many species will rebound. Others may be replaced by even more heat adapted species from Mexico.

But even though collection numbers in terms of species as well as individuals were low, I did succeed to complete my virtual collection of the genus Euphoria in the subfamily of  the Flower Chafers, Cetoniinae this year. These are day-active scarabs that fly extremely well with their hard wing covers (first wing pair) closed. A sneak preview of Bill Warner's yet unpublished Checklist of Arizona Scarabaeoidea confirmed that the ten species below are the ones that I can hope to find.

Euphoria Species of Arizona
 
Since I prepared this table, there has been a revision of the genus Euphoria and some names have been changed: E. fulgida holochloris is now E. monticola .  E. fascifera trapezium is now simply E. fascifera, E. kernii was always spelled like this, E. histrionica is now  E. sonorae

Usually I try to photograph living beetles, but I was also delighted to have access to the beautiful and rather complete collection of Patrick Sullivan in Sierra Vista. The specimens of Euphoria devulsa and E. canescens were photographed in this collection. Even Pat's representative for E. canescens came from Mexico, but Barney Streit told me that E. canescens can be found on Sunflowers along  Duquesne Road,Cochise County, Arizona.


E. kernii, which is so common on Opuntia and Prickly Pear flowers further east (Texas), is found in Arizona in a light and a nearly black morph and seems fairly rare.


E. quadricollis (E. arizonica) female and male

E. quadricollis, synonym E. arizonica, 'is sexually dimorphic, with the females tending to be shiny, broader and much darker than the more gracile, tomentose males. The amount of dark spotting on both sexes is variable, but usually much less in males' (Bill Warner via email). Females seem to be less represented in collections which led to some questions about the identification of the female that I found on a tree stump at Copper Canyon, Cochise Co.The image of the male is of a specimen curated at the collection of the University of Arizona.

Euphoria verticalis
E. verticalis, which used to be in the genus Stephanucha when I collected my first specimen in 2007, apparently flies after both rainy seasons: Eric Eaton caught the first one this year in early April when it was buzzing knee-high along stands of wild flowers in Sabino Canyon. In late September I usually find dozens around Annual Sunflowers at the Santa Cruz River and on Desert  Broom bushes in Molino Basin.


  Euphoria leucographa (sepulcralis rufina)


Every year in late summer,  Desert Broom is also the best place to find Euphoria leucographa, our most common Euphoria. With many other insects, the beetles enjoy the sweet juices oozing from the bark of this bush after generous monsoon rains. In October they also frequent the Desert broom flowers.



Euphoria sonorae (histrionica)

 I collected the similarly patterned, smaller E. sonorae in the Huachucas, from lower Carr Canyon to the very top of Miller Canyon. These beetles bury deeply into the flower disc of Sunflowers. This is so typical for them that they can be recognized immediately by their protruding hind ends.



Euphoria inda



I have encountered E. inda only once, at the research Station in Portal buried in flowers of milk weed and then flying off to the mesquite where I photographed it. B. Streit found it west of Portal in thistle flowers.
About this species, Art Evans has an interesting story to tell in his blog - how a specimen made it all the way to Africa to be described there as a newly discovered genus, until Art found it in the South African Museum in Cape town  and dismantled its cover.







 E. monticola (fulgida holochloris) is a great imitator of Carpenter Bees. Like the bees, it spends a lot of time on the wing without landing. when the beetle is buzzing by at high speed the closed shiny fore-wings give a perfect impression of the bee's heavy, dark body.
 Euphoria monticola (photos D. Danforth)





In July and August, I've seen them in the Chiricahuas and the Canelos in similar forested areas under oaks where the ground was covered in moist leaf litter. The male beetles seem to patrol certain paths and clearings, never flying more than a few feet high, probably in search of females on or in the ground. Females are hardly ever collected

Euphoria fascifera trapezium 

 E. fascifera trapezium, which I knew from California, is reported occasionally from our lower desert areas, supposedly associated with pack rat nests. This year it was observed in Tucson in early summer. It seemed to be feeding on fresh Mesquite pods that were bleeding after Mesquite Bug infestation. I finally got hold of one in October when Bruce Mitton collected it for me on blooming Rabbit Bush in his yard in North West Tucson where they regularly breed under his raised planters with lots of composted manure.

The life cycle of this genus is not well described. There seem to be one to two generations per year. The phytophagous larvae have been found in the ground under cow dung and in ant hills. Some adults are reportedly associated with gopher and pack rat nests. Adults feed on pollen, tree-sap, sweet fruit. They have been known to invade bee hives. Rarely, they become pests, damaging young corn or the flowers of roses or mango.