Sunday, September 14, 2014

A Jumping Spider, Tutelina similis

When my wife and I were in Atlanta back in June of this year, I had the opportunity to walk from our downtown hotel out to the Fernbank Natural History Museum along a route prescribed by one of the Google services. Taking a detour into a wooded ravine along a creek led to the discovery of a lovely little jumping spider, Tutelina similis.

Since signing a contract to do a new field guide to U.S. spiders for Princeton University Press, I have been crafting a species list. Upon first spotting a male T. similis I thought to myself: "That is not on my list. It sure is now!" I had no idea at the time exactly what it was, other than a member of the Salticidae, but its bold, attractive markings made it stand out.

What are we looking at when we stare into the face of one of these? Well, the pedipalps are the most obvious feature. Those are the short, leg-like mouthparts. In this case, they are black on the outer half, with a fringe of long white hairs on the inner half. The palps usually hide the chelicerae (jaws) unless the spider drops the palps and raises its "head" (cephalothorax). This species also appears to have "eyebrows" in the form of short black lines on the cephalothorax immediately behind the very large anterior median pair of eyes. It makes the spider appear to be in a state of perpetual surprise (or anger, depending on your viewing angle).

Despite their small size (4.0-5.0 millimeters body length), these are pretty conspicuous spiders that in this case were prowling understory vegetation about three to four feet off the ground. The sunlit patches where the deciduous tree canopy opened up seemed to be a favorite hunting ground. Indeed, insect activity peaks in these situations where flies, wasps, bees, and other potential prey bask, and defend territories.

Browsing through, I was able to identify this species. My friend Troy Bartlett had even photographed a few. The overwhelming number of records on that website are from the month of June, so apparently the spiders mature at that time.

Like most jumping spiders, this species exhibits sexual dimorphism. That means that mature males differ markedly in appearance from mature females. I did not find any females myself, but below is an example of one from Hastings, Ontario, Canada, via The females are slightly larger than the males, but not dramatically so.

© Jason King

Tutelina similis is transcontinental in its Canadian distribution, and ranges east of the Rocky Mountains in the U.S. to at least Georgia and New Mexico. It has been found on mailboxes in rural Massachusetts (Edwards & Edwards, 1997), and in the seedheads of pitcher plants in Maine (Jennings, et al., 2008).

At least one population of this species in Utah was found to be a specialist predator on ants, even mimicking ants in color and behavior as it prowled over sagebrush. The front legs of these arachnids are waved about in the manner of ants waving their antennae (Wing, 1983).

It is species like this that make jumping spiders a favorite among people who study spiders. The wide-eyed stare and curious nature of salticids is enough to melt the heart of the most extreme arachnophobe, and endear them to gardeners and homeowners who might level a shoe at any other arachnid. Couple that with the extraordinary hunting skills that make jumpers heroes in the war on pests, and you have pretty much the poster child for why we should embrace spiders as a whole.

Sources: Edwards, Robert L. and Eric H. 1997. "Behavior and Niche Selection by Mailbox Spiders," J. Arachnol. 25: 20-30.
Jennings, Daniel T., Bruce Cutler, and Bruce Connery. 2008. "Spiders (Arachnida: Araneae) Associated with Seed Heads of Sarracenia purpurea (Sarraceniaceae) at Acadia National Park, Maine," Northeastern Naturalist 15(4): 523-540.
Richman, David B., Bruce Cutler, and David E. Hill. 2012. "Salticidae of North America, Including Mexico," Peckhamia 95.3: 1-88.
Wing, K. 1983. "Tutelina similis (Araneae: Salticidae): An Ant Mimic That Feeds on Ants," J. Kans. Entomol. Soc. 56(1): 55-58.

Wednesday, September 10, 2014

A Spider Wasp, Aporus luxus

When I lived in Oregon, one of the most common spider wasps I encountered was a lovely little iridescent blue-black species, Aporus luxus. My wife and I traveled to Oregon earlier this year, and on July 12 I found the two specimens pictured here at a rest stop on Interstate 5.

One of the easiest ways of identifying the seven members of the genus Aporus is by the way the front of the thorax slopes gradually toward the head, giving a very streamlined appearance. The front legs are short, and indeed all the legs are proportionately shorter than in other spider wasps. The antennae are relatively short and thick, a trait they share with the unrelated genus Evagetes, but the latter has a much blockier thorax.

At only 8-15 millimeters in body length, these are not large insects that are apt to attract your attention in the field, but they are common wasps on flowers of Queen Anne's Lace (aka Wild Carrot), Daucus carota, and other umbelliferous blossoms that afford the wasps nectar and an unobstructed view of potential incoming danger. While thus occupied they are fairly easy to approach. Constantly moving, they still make a challenging target for photography.

Aporus luxus has also been found on flowers of buckwheat (Eriogonum spp.), rabbitbrush (Chrysothamnus spp.), gumweed (Grindelia spp.), spurge (Euphorbia spp.), Woollyhead Parsnip (Sphenosciadium capitellatum), sweetbush (Bebbia sp.), elderberry (Sambucus spp.), mesquite (Prosopis spp.), Desert Willow (Chilopsis linearis), and saltcedar (Tamarix spp.). The wasps also visit the extrafloral nectaries of Common Sunflower, Helianthus annuus, and the honeydew secreted by aphids, and exudates of galls on oak trees.

The life history of the larval stage is almost wholly unknown. An adult male wasp was reared from a wafer-lid trapdoor spider, Aptostichus sp., in the family Euctenizidae. The spider is stung into paralysis by the adult female wasp, and she utilizes the spider's own burrow as her nest, depositing a single egg on her victim. There is only one generation in most cases, though in southernmost latitudes there are apparently two generations annually.

This species ranges from central British Columbia to central Baja California, eastward to western Idaho and Utah, and most of Arizona. There is one record from Montezuma County, Colorado (Evans, 1997). Adult specimens are most common between the months of May and October.

Sources: Evans, Howard E. 1997. "Spider Wasps of Colorado (Hymenoptera, Pompilidae): an Annotated Checklist," The Great Basin Naturalist 57(3): 189-197.
Fensler, Nick. 2006. "Genus Aporus,"
Wasbauer, M.S. and L.S. Kimsey, 1985. "California Spider Wasps of the Subfamily Pompilinae," Bull. of the California Insect Survey vol. 26. Berkeley: University of California Press. pp. 1-130.

Friday, September 5, 2014

Great Crested Grasshopper

Yesterday was "OrThoptera Thursday" in the truest sense. I had the car at my disposal, thanks to my wife and a co-worker carpooling, so I drove out into the rural plains of eastern El Paso County in search of grasshoppers. This was the first time since my arrival in Colorado that I simply went out walking in the vast shortgrass prairie east of Colorado Springs. Much to my delight, I managed to find the creature at the top of my list: the Great Crested Grasshopper, Tropidolophus formosus.

This species is also known as the "dinosaur grasshopper" for the resemblance of its pronotal crest to the fin-like structure on the back of Dimetrodon dinosaurs. The grasshopper's crest is studded with fine, prickly teeth on the rear half, barely discernible in the images shown here.

These are large insects, adult males attaining a length of 35-46 millimeters, and female 38-50 millimeters. Males are fully-winged, but the wings of the female are short, barely extending half the length of the abdomen. Despite their size and ungainly appearance, they are wary and surprisingly agile, not to mention cryptic. The only way I managed to find them was by flushing them from the vicinity of dense vegetation and hoping I could follow their flight path. I never did find a female.

The Great Crested Grasshopper is one of the band-winged grasshoppers in the subfamily Oedipodinae, family Acrididae. The hind wings are a lovely vermillion, with a diffuse dark band near the wing margin, as shown here. In flight the species is not easily confused with other red-winged grasshoppers.

The references I have consulted indicate that males have a noisy flight, especially in courtship displays, but all the individuals I encountered flew silently....and far. Invariably, it seemed, they always flew to the other side of the barbwire fence.

The preferred food of this grasshopper is apparently globemallows, (Sphaeralcea spp.), Malvastrum, and other members of the family Malvaceae. It has also been found in association with Buffalo Bur, Solanum rostratum. Because it does not favor crop plants or rangeland forage consumed by cattle, the Great Crested Grasshopper is not considered a pest species. Further, it is not terribly abundant. I found a grand total of about eight or ten specimens yesterday, in hours of looking.

Tropidolophus formosus is not widely distributed, found mostly in the southern Great Plains, but ranging from southeast Wyoming and southwest Nebraska south through eastern Colorado, western Kansas, Oklahoma, and Texas, eastern New Mexico, and southeast Arizona. It is also found in northwestern Mexico. Adult specimens can be found from July through October across that area.

The plains and prairies may seem devoid of life except for the occasional herd of deer, pronghorn, or bison, or soaring hawk, but look closer and you will find an abundance and surprising diversity of life, from reptiles (two lizards and one snake for me yesterday) to insects. I encourage you to explore that biome, and do so often. The animals you find will vary dramatically depending on drought or monsoon conditions.

Sources: Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca: Comstock Publishing Associates (Cornell University Press). 249 pp.
Helfer, Jacques R. 1972. How to Know the Grasshoppers, Cockroaches, and Their Allies (2nd ed.). Dubuque, Iowa: Wm. C. Brown Company Publishers. 359 pp.

Tuesday, September 2, 2014

Sundew Assassin Bugs: Zelus

Your garden is full of amazing predators, easily overlooked among the foliage and flowers. No matter where you live in the U.S. and southern Canada, save perhaps for the northern Rocky Mountains, you probably have sundew assassin bugs of the genus Zelus lurking in the yard. These leggy insects move slowly about, or wait in ambush for potential prey.

Zelus luridus female, Colorado

There are currently five recognized species of Zelus north of Mexico, most with wide geographic distributions. Few are readily identifiable to species just by looking at them, but common ones include: the lovely green Zelus luridus with a sharp spine on either side of its thorax; the bright red and black Milkweed Assassin Bug, Z. longipes found in the southeast U.S.; and the non-descript Z. tetracanthus with its four small "knobs" across the top of its thorax. The Leafhopper Assassin Bug, Z. renardii, is common in the southwest U.S. and has been entertained as a potential biocontrol agent for pest reduction in agricultural settings.

Zelus longipes, South Carolina

Sundew assassins get their common name from the unique physiology that allows them to catch prey. While ambush bugs have extremely muscular front legs that snap shut on prey with stunning force, sundew assassins look like the 90-pound weakling by comparison. Their appendages are thin and seemingly delicate or flimsy. The tibiae ("shins") of the front legs (and to some degree the middle legs) are densely covered in short hairs, and this is part of their secret weapon.

Zelus tetracanthus, Colorado

Special glands in the exoskeleton of the legs secrete a glue-like material that that the insect intentionally smears over those hairs. This creates a sticky layer that small prey cannot escape from once the assassin grabs them. The prey-catching scenario is analogous to the insect-eating plant known as the sundew, which inspires the name "sundew assassin bugs."

When they hatch from the egg, nymphs do not have the ability to produce the glue they need. No matter, mom has covered the egg cluster in sticky goo to help repel egg parasites like tiny wasps, and the nymphs simply wipe their "arms" along the base of the egg mass to gather some glue (Weirauch, 2006).

Zelus luridus nymph, Colorado

Nymphs go through five instars (an instar is the interval between molts) on their way to adulthood. They are noticeably larger after each molt, with wing pads evident in the last couple of stages.

Zelus hatchlings

The egg mass reminds me of a tiny crème brûlée, but perhaps I need to eat lunch and return to finish this post later....I was delighted to stumble upon a couple of egg masses in the act of hatching at the Cheyenne Mountain Zoo here in Colorado Springs back on July 21. It seems remarkable that such long-legged creatures could be packaged in such small vessels.

Zelus hatchlings

There are at least two generations annually here along the Front Range in Colorado, probably three or more generations in southerly latitudes. I notice nymphs of Z. luridus in spring, so it is likely that winter is passed in the egg stage.

Zelus species range from 14-21 millimeters in body length as adults, and are relatively easy to recognize with their slender build, long legs and antennae, and diurnal period of activity. They are largely arboreal, so you will find them mostly on foliage and flowers of trees, shrubs, and herbs.

Zelus renardii, Texas

Assassin bugs in general are indiscriminate predators of other insects, and Zelus is no exception. So, while they will dine on leafhoppers, small caterpillars, and other pests, they will also capture beneficial insects such as small bees.

Despite our tendency to classify insects as "good" or "bad" for our own selfish reasons, sundew assassin bugs should be welcomed for the benefits they provide in occasional pest control, and their unique behavior and "personality," if I dare use that word for an invertebrate.

Zelus luridus male, Colorado

Sources: >Valerie. 2014. "Reduviidae ~ Assassin Bugs," Austin Bug Collection.

Weirauch, C. 2012. "Taxonomic Revision of Zelus Fabricius," Heteropteran Systematics Lab @ UCR
Weirauch, C. 2006. "Observations on the sticky trap predator Zelus luridus STÅL (Heteroptera, Reduviidae, Harpactorinae), with the description of a novel gland associated with the female genitalia," Denisia 19, zugleich Kataloge der OÖ. Landesmuseen Neue Serie 50 (2006), 1169-1180.
Wolf, Klaus Werner and Walton Reid. 2001. "Surface Morphology of Legs in the Assassin Bug Zelus longipes (Hemiptera: Reduviidae): A Scanning Electron Microscopy Study With an Emphasis on Hairs and Pores," Ann. Entomol. Soc. Am. 94(3): 457-461.