Wasp Wednesday: A Real Surprise

I am certainly finding the Front Range region to be exceptionally diverse when it comes to wasps, but nothing could have prepared me for what I found in the field yesterday, August 7. I was looking over a White Sweet Clover (isn’t there a song about that?), when a very large wasp commanded my attention. I immediately recognized it as a paper wasp, but not a species I would have expected in Colorado Springs.

This is a male specimen of Polistes carolina or Polistes perplexus. Either way, it is most likely going to turn out to be a county record, potentially a state record, and perhaps even a range extension. Both species are recorded for Kansas, so what is a couple hundred more miles or so?

I also managed to collect the specimen, so I’ll be able to eventually examine it under a microscope for the details necessary to separate the two species. Until very recently, it was thought that the males could not be distinguished at all, but apparently there are transverse (horizontal) ridges on the propodeum (hindmost segment of the thorax) that are weak in P. carolina and much more evident in P. perplexus. Watch this space for the final determination of the species.

For now, I’m ecstatic over this discovery. I’d sure like to find the nest this fellow came from. Females are a little easier to identify, and finding the nest would verify that this is a species breeding here. Even so, this male is in immaculate condition, suggesting it did not travel a long distance.

Because these two species were once thought to be a single species (P. carolina), most documentation of their biology is somewhat suspect. Polistes carolina apparently nests in exposed situations, such as under the eaves of buildings, for example; and reports of that species nesting in hollow trees and other protected locations actually apply to Polistes perplexus. Prey is probably similar in both species, consisting mostly of caterpillars chewed up by the adult wasps and fed to the larvae in the nest. Still, wasps this large can probably tackle much larger prey, and a single record of an attack on a cicada (Tibicen auletes) could be for either species of wasp.

I find that in current literature the size of these wasps is measured by the length of the forewing, which is 15-20.5 millimeters in P. carolina, and 17-21.5 millimeters in P. perplexus. Contrast this with the measurements of the abundant and widespread Northern Paper Wasp, Polistes fuscatus. Forewing length for that species averages between about 13 and 17 millimeters.

Polistes carolina is most common in the southern U.S., but ranges from New York, Pennsylvania, and Ohio south to Florida and west to Illinois, Kansas, Arkansas, and eastern Texas. There is one record for Ontario, Canada, but the species is not established there. That could be the case here in Colorado, too: a fluke. P. perplexus ranges from Maryland to Georgia, and west to southern Illinois, Kansas, Oklahoma, and Texas. One recent record has come from Pennsylvania.

Keep your own eyes open for species that seem “misplaced.” Interstate (and international) commerce, climate change, and other factors are changing the distribution patterns and abundance of many species. We also haven’t looked that closely at insect species with little or no economic impact. You stand a good chance of adding to our collective knowledge with relatively minimal effort.

Source: Buck, Matthias, Stephen A. Marshall, and David K.B. Cheung. 2008. “Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region,” Canadian Journal of Arthropod Identification No. 5: 492 pp (PDF version).

Time to Delete "Moth" From Our Vocabulary

I recently learned of a controversial theory of metamorphosis that got me thinking about moths and butterflies. More on that later. Perhaps National Moth Week also had something to do with my thought process, and/or a Facebook post by a friend purporting a difference between moths and butterflies. Folks, there is no such thing as a difference between moths and butterflies.

There is no difference between moths and butterflies that does not have exceptions:

• Moths have feathery antennae. This is a myth. A few do, the males’ more “feathery” than the females’, the better to detect her pheromones wafting on the winds. Most moths have filamentous (hair-like) antennae.
  
• Moths are active at night. Hogwash. Most species are nocturnal, but there are plenty that fly during the day. Many fly both day and night. There are some butterflies that are nocturnal for that matter. I have personally seen some hairstreak butterflies attracted to lights at night.
  
• Moth caterpillars spin cocoons. Hardly any moth caterpillars spin cocoons, actually. Most simply have a naked pupa (the term “chrysalis” could also apply), often underground, sometimes inside a gallery the caterpillar bored in dead wood or living stem, stalk, or root. A cocoon does help insulate a pupa in exposed situations during weather extremes, so some species add this silken covering.
  
• Moths eat clothing. There is so much wrong with that statement I’m not sure where to begin. The larvae (caterpillars) of some moths do consume dried animal products like wool garments and blankets, but they are in an extreme minority. The feeding habits of the vast majority of moth caterpillars are of no consequence to people whatsoever.

It is that last item that hints at the real reason we insist on an artificial distinction between moths and butterflies. We need a villain, and the moth is it. Butterflies can do no wrong! They are colorful and carefree and their larvae eat weeds we don’t like. Moths are evil, their caterpillars consuming our crops and ravaging our forests. Moths are black, brown, or gray, and hide themselves in shame by day, only daring to emerge under the cloak of darkness that is night.

Moth Week may have started to peck away a little at the mythology of moths, but we should consider banishing the term “moth” from our lexicon altogether. Science recognizes that weevils, “ladybugs,” and “fireflies” are all types of beetles. Mosquitoes, gnats, and no-see-ums are acknowledged as types of flies. Moths are butterflies, by virtue of the fact that they are in the same order: Lepidoptera.

The theory of metamorphosis that made it onto National Public Radio implies that it isn’t butterflies and moths that are different, but the adult stage and the caterpillar stage. So different are they that perhaps they are separate species merged into one being. The caterpillar leads an entirely different lifestyle than the adult, and “dies” during the pupal stage, only to be “resurrected” as a new, winged creature at the conclusion of the life cycle. Yes, the majority of the scientific community scoffs at this idea, perhaps rightly so, but one can argue that the similarities between adult butterflies and moths are much smaller than the differences between the larva and adult of any one species.

Moths need positive attention for many, many reasons:

• Scores of moth species are endangered, or have populations that truly border on unsustainable. Contrast that with the “sky is falling” cries from butterfly conservationists every time there is the slightest slump in populations of hibernating Monarch butterflies.
  
• Moths are true pollinators, while butterflies (and many moths, to be fair) are merely “flower visitors.” Female yucca moths (family Prodoxidae) intentionally stuff a wad of pollen into the stigma of the host plant, thereby fertilizing it. The moth does this because her caterpillars require viable yucca seeds on which to feed. The caterpillars rarely consume the entire seed set, and both host and herbivore prosper. Several tropical orchid species rely solely on certain sphinx moths for pollination.
  
• Moths are incredibly important to the food chain. Countless birds, bats, even grizzly bears, rely on moths as a food source. Oh, add fish, reptiles, amphibians, spiders, and other insects to that list. Many of those predators are in fact moth specialists. Some spiders even mimic the pheromones of certain female moths to attract the male moths to their webs.

It is time to call “moths” what they really are: butterflies. Time to stop discriminating based on assumptions, myths, and preconceived notions of what moths should be. Reality is far more subtle, and nature lacks the anthrocentric lens we view Her through. Our vocabulary should reflect that reality, and not our prejudice, cynicism, and biases. Who is with me?

Spider Sunday: Sixspotted Orbweaver

I like to investigate sunflowers (Helianthus sp.) at this time of year because the plants’ extrafloral nectaries attract a variety of wasps, flies, and other insects. Not surprisingly, predatory insects stake out sunflowers, too, taking advantage of the abundance of potential prey. One of those predators that I found the other day was a Sixspotted Orbweaver, Araniella displicata.

This particular specimen was the color of a sunflower, too, with a bright yellow abdomen. Other specimens, as illustrated throughout this post, may be nearly pure white, or infused with varying degrees of rust red, especially in immature specimens. The species does maintain a consistent pattern of three (sometimes four) pairs of black dots along the edges of the rear half of the abdomen.

The Sixspotted Orbweaver is one of the most widely-distributed arachnids in North America, found over virtually the entire continent, including parts of Alaska. It is not uncommon in gardens and yards, but neither is it conspicuous. Adult females measure only 4-8 millimeters in body length, males 4-6 millimeters.

Most orb weavers spin fairly large webs in proportion to their own body size, but not so with Araniella displicata. The web of an adult spider may be only three or four inches in diameter. The spiral snare is usually built well off the ground (four to six feet), and often oriented in the horizontal plane, frequently spanning the edges of a single large leaf. The spider sits in the center (hub), hanging beneath a horizontal web (as in the image above), or head-down in a vertical one. Webs spun across the edges of a leaf may intercept and entangle longlegged flies (family Dolichopodidae), and other insects that habitually skitter over the surface of a leaf and then take flight to another piece of foliage.

Sixspotted Orbweavers overwinter as subadult spiders, reaching adulthood in late May or early June (probably earlier in the more southerly climates). Mating takes place at about that time, and female spiders make egg sacs shortly thereafter. The egg sac contains an average of 80 eggs and is covered in loose, fluffy, yellowish silk. The package may be deposited in a curled leaf that also serves as the mother’s retreat on the perimeter of the web.

Interestingly, while this species tends to frequent woodland habitats in North America, it is found mostly in heath and heather fields in Britain, where it also occurs. The species ranges over much of northern Europe but is considered rather uncommon or even rare.

The next time you find a “baby” orb weaver, be sure and check to see if it might not actually be an adult of Araniella displicata. Mature ones can be found from late spring to nearly the end of summer. After that, you will find juveniles.

Sources: Howell, W. Mike and Ronald L. Jenkins. 2004. Spiders of the Eastern United States: A Photographic Guide. Boston: Pearson Education. 362 pp.
Weber, Larry. 2003. Spiders of the North Woods. Duluth, Minnesota: Kollath+Stensaas Publishing. 205 pp.

Wasp Wednesday: Bembecinus

Once again, just last Saturday, July 28, I found myself baffled by a little wasp I found excavating a burrow in some sand not far from my home. I took images and, realizing that I didn’t recognize it, began the identification process. I started with something it reminded me of: a small Bicyrtes species. I then went up the classification ladder on Bugguide.net. How about the subtribe Bembecina? Not really, though Microbembex was close. Was it in the tribe Bembicini at least? Yes, that seemed like a safe bet. Browsing the images for the subtribes I found myself surprised that the Stizina looked promising. Indeed, it turns out I had been observing a female wasp in the genus Bembecinus.

The characters I found key to making the ID included the eyes, which are strongly convergent at the bottom of the face, and strongly divergent at the top of the head. The second submarginal cell in the front wing is petiolate or nearly so.

I thought I had lost my opportunity to photograph this wasp right off the bat. I made a quick move while she was down her burrow, but she popped back out quickly, saw me, and flew off. Luckily, she was determined to finish what she started, and returned shortly to continue digging. She would occasionally fly off, only to return a short time later, regardless of my presence or movements. At one point a tiny, curious ant walked into her burrow while she was inside it, and she literally kicked it out of her tunnel.

Good thing for the ant that female Bembecinus hunt leafhoppers (Cicadellidae and related families) as food for their larval offspring. Rather than stockpiling several prey and then leaving the larva to feed, Bembecinus practices an advanced form of parental care called “progressive provisioning.” She lays her egg in the empty cell at the end of her burrow, and then brings food to the larva on an as-needed basis. She can deliver, too. Researchers have recorded different species bringing in from 71 to 757 prey items to a single nest. One assumes the larger the prey species the fewer it takes to feed the wasp larva, but that is still a staggering amount of work for the mother wasp.

The burrow is eventually sealed permanently at, or before, the time the larva enters a pre-pupal stage. The female then begins the nesting process over again. Bembecinus is often highly gregarious, several to many individual females nesting in a small area. Indeed, I did find another specimen (though perhaps a different species) nesting nearby the first.

Interestingly, males of some species of Bembecinus actively dig to reach pre-emergent, virgin females. These males have short “tarsal rakes” of spines on their front feet, so may be mistaken for females themselves. They are among the most competitive of wasps when it comes to mating, and males may physically fight over a female at any point, including when another male is already coupled with a female.

Both genders gather in “sleeping clusters,” sizeable balls of wasps situated on twigs, stems, or foliage of plants near the nesting area. The clusters can be all males early in the season, and all females late in the season, though this varies with the species and maybe even the geographic area.

Bembecinus is not immune to nest parasites. Velvet ants (family Mutillidae), and cuckoo wasps (Chrysididae) have been recorded as parasites for different species of Bembecinus around the globe. Surprisingly, no fly parasites have been documented. Satellite flies in the family Sarcophagidae are insidious pests of most all other burrowing wasps, so this is a mystery.

There are currently ten species of Bembecinus listed for North America north of Mexico, collectively found across most of the continent. Approximately 190 species are known worldwide, on all continents but Antarctica. The specimens I was watching measured an estimated 8-10 millimeters in size, but some species are larger and others smaller.

I may have to go back and see if I can find more of these interesting sand wasps. I hear they are even active on extremely hot days, and we have had a lot of those this year in Colorado Springs.

Sources: Evans, Howard E. 1966. The Comparative Ethology and Evolution of the Sand Wasps. Cambridge, Massachusetts: Harvard University Press. 526 pp.
O’Neill, Kevin M. 2001. Solitary Wasps: Behavior and Natural History. Ithaca: Comstock Publishing Associates (Cornell University Press). 406 pp.