Monday, July 30, 2012

Look-alike Leps, a Carnivorous Caterpillar and Large Larvae

Apt to be found nectaring at milkweed blossoms on sunny June days, the Banded Hairstreak (Satyrium calanus) is one of our most frequently encountered Lycaenid species.

The following image of a Banded Hairstreak caught my eye as I was reviewing the files on my hard drive. Individual Banded Hairstreaks can certainly vary in appearance but this seemed like a rather extreme departure from the norm. After doing a bit more reading and research, methinks this is the much less common Hickory Hairstreak (Satyrium caryaevorum).

A word of caution: relying on appearance alone to identify insects to the species level is undependable, and I could well be wrong ... the correct procedure is to capture a specimen and examine the genitalia. Having said that, here are the criteria for separating the Banded Hairstreak and Hickory Hairstreak at – Butterflies of Canada ... Hickory Hairstreak

At first glance the Striped Hairstreak (Satyrium liparops) can be mistaken for one of its cousins (including the Edwards' Hairstreak, I don't have a photo of this species so here's a link to Butterflies and Moths of North America). However, the bands on this small butterfly's wings are much more widely spaced, the blue spot on its hind wing is capped with orange, and – said hindwing sports two distinct tails.

Changing the subject from befuddling little gray butterflies to confounding small green moths ...

A Blackberry Looper (Chlorochlamys chloroleucaria) encountered in late May. The upper surfaces of the bluish-green wings appear granulated and they have a white fringe around their borders. This moth is a female; the male has bipectinate (comb-like toothed margins on both sides) antennae.

All four wings of the Showy Emerald (Dichorda iridaria) have discal dots, distinctly green-bordered white lines, and clean, sharp edges.

An anterior view of the Showy Emerald ... the top and front views rule out the possibilty that this is a Red-fronted Emerald (Nemoria rubrifrontaria) or a Red-bordered Emerald (Nemoria lixaria).

Since the considerably smaller hindwings are challenging to position when pinning this moth, collectors have dubbed it The Bad-Wing (Dyspteris abortivaria). Also note the rounded appearance of the wings, and the small white discal dots on the front wings.

So where, you might ask, is the dreaded "Carnivorous Caterpillar" mentioned in the title? Sorry to say, I don't (yet) have a picture of a creepy (not to mention deviant) caterpillar chowing down hapless, helpless little bugs.

The larva of the Harvester (Feniseca tarquinius) does have the unique distinction of being the only Canadian caterpillar that feeds on other insects, specifically Woolly Aphids. The roots of the name Lycaenidae lie in the Greek word for wolf, so at least in the case of this butterfly the family name is apropos, it is – in a manner of speaking – an "aphid wolf".

I almost managed to overlook this huge – close to 90 mm in length – boldly marked caterpillar sitting on a Virginia Creeper. This is the last (fifth) instar larva of the Pandorus Sphinx (Eumorpha pandorus). In addition to Virginia Creeper this species of sphinx moth also feeds on the leaves of grapes.

Pandorus Sphinx caterpillars lose the typical sphinx moth caudal horn as they grow and molt. Is the prominent black, red and white nub that remains meant to be a target, directing a predator's attention away from the head (to the right) toward a non-vital area of the body?

Feeling threatened by my proximity the cautious caterpillar has not only withdrawn its vulnerable head into its own fashionable turtle-neck collar, it is blowing bubbles from its mouth ... is this a noxious fluid that deters predators?

The day after I encountered the Pandorus Sphinx caterpillar, I stumbled across a Waved Sphinx (Ceratomia undulosa) larva near the same tree. I'm not using "stumbled across" as a figure of speech ... the insect was crawling on the ground and I almost stepped on it.

The caudal horn – a sphinx moth caterpillar trademark.

Judging by its size this is also probably a fifth instar caterpillar and ready to pupate any time; it measured a good 100 mm in length and easily spanned the palm of my hand. The preferred host plant of the Waved Sphinx is ash, but they will also eat oak, hawthorn and lilac.

Friday, July 27, 2012

It only took about 300 million years ...

... for the forces of natural selection to produce spiders. Silk-producing arachnids go back even farther (nearly 390 million years), and chelicerates – distant cousins of spiders – were among the first animals to leave the sea and conquer dry land. Of the roughly 40,000 species of spiders in the world about 5,000 belong to the family Salticidae, the jumping spiders.

Jumpers are fun spiders to watch. Unlike the orb weavers which simply hang in the middle of a web waiting for a meal to come to them, jumping spiders actively hunt for their dinner – they almost seem to have character. The sturdy female spider in the next two pictures is a Phidippus whitmani. A photo of a male, which is a striking bright red rather than brown, would have brightened up the color scheme.

The average Phidippus clarus in my area also tends to be a rusty brown but this summer I was lucky and stumbled across several males that were a beautiful red. It's tough to get a dorsal shot of that abdomen, as jumping spiders have a habit of facing toward the camera, aiming those arresting anterior median eyes at whatever they perceive to be a threat. See what I mean about character?

Phidippus clarus is a good sized jumping spider about 10 mm long, my finger to the left in the photo gives a sense of scale.

A male Marpissa formosa basking on the rocks along the river shoreline, also about 10 mm in length but elongated and lean rather than robust.

I was at unable to identify the male spider in the following three images. Despite its length of 6 mm and the shape of the carapace being completely wrong, I nevertheless – tentatively, reluctantly, unhappily – called it a "crab spider" (male crab spiders are tiny, much smaller than 6 mm). This diagnosis was less than satisfactory so I submitted the images to the always helpful people at BugGuide.Net, and it turns out that my "crab spider" is an old friend ...

... Araneus trifolium, the Shamrock Orbweaver. (The little red hitchhiker on the spider's abdomen is a parasitic larval mite, family Erythraeidae.) As is often the case with spiders the male is much smaller than the female, the old girl in the photo below is a good 25 mm in length, and gravid, ready to lay eggs any time. Talk about sexual dimorphism ... looking at these two spiders, who would guess that they were the same species?

This is a white form female, and if the difference between the male and female aren't enough to cause confusion, female Shamrock Orbweavers, a.k.a Pumpkin Spiders, come in an awesome array of colors!

Whilst they don't come in a baffling variety of tints and hues, Flower Crab Spiders such as Misumena vatia can change their color from yellow to white in order to match the color of the flower they are lurking on. Obviously the Flower Scarab (genus Trichiotinus, itself an accomplished bee mimic) is unaware of how perilously close it is to its possible demise ...

Although many species of wasps are parasitoids of spiders, the Thread-waisted Wasp (Ammophila sp.) provisions its larvae with caterpillars and this wasp was simply stopping at these False Solomon's Seal blossoms for drink of nectar, not hunting the spider as a potential source of nourishment for its young.

But Flower Crab Spiders blend into the background so well they are virtually invisible, nature seldom forgives errors in judgement, and unlike the Flower Scarab this wasp wasn't so lucky. The Thread-waisted Wasp won't be passing on its genes to the next generation, the Flower Crab Spider might – if it survives the hazards and vicissitudes of an uncertain life – and who knows ... her descendants may still be around in another 300 million years.

Tuesday, July 24, 2012

An Eclipse of Moths

The origin or etymology of this turn of speech describing a group of moths is, no pun intended, obscure. Perhaps its origins can be attributed to the dull, cryptic coloration of many moth species, but eclipse is the last word that comes to mind when one encounters moths which use color to attract a mate visually, or sport eyes-spots or other startle patterns, or are toxic or distasteful and display aposematic colors to advertise their unpalatability.

Hiding in plain sight ... oddly enough, the eye-catching pink wings of the Primrose Moth (Schinia florida) actually seem to help it blend into the background. It was surprisingly difficult to pick out these moths nectaring at their favorite flower, which also serves as the larval host plant.

Tiger Moths, Lichen Moths and other members of the subfamily Arctiinae are often day fliers and tend to be quite colorful. An interesting characteristic of this group of moths is family is a tymbal organ on the metathorax, thought to be a sonic countermeasure against bat's echolocation systems.

Aposematic ... from Greek, apo → away, and sematic → sign or meaning.

The feathery antenna indicate this is a male Virginia Ctenucha (Ctenucha virginica) ...

... often confused with the Yellow-collared Scape Moth (Cisseps fulvicollis). Here's a link to the Cisseps fulvicollis page at BugGuide.Net. Good information, but it doesn't answer a question that's been "bugging" me – are the clashing colors a Batesian bluff, or an aposematic alert? The moths' vivid orange and iridescent blue paint job (and manner of flight) does impart a wasp-like aspect ... or ... is it meant to tell hungry eyes "I'm poisonous!"?

The bold colors of the Black-and-yellow Lichen Moth (Lycomorpha pholus) are presumed to mimic the distasteful Net-winged Beetles (family Lycidae).

To be sure, the Lichen Moth is a pretty good facsimile of the End-Banded Net-Winged Beetle (Calopteron terminale). But I am puzzled ... my understanding is that in order for Batesian mimicry to be successful, the population of models (in this case the Net-winged Beetle) must be greater than the number of mimics (Lichen Moth). Yet from what I have observed, there are a lot more Lichen Moths than Net-winged Beetles out there ...

Caterpillars of the brilliant Scarlet-Winged Lichen Moth (Hypoprepia miniata) feed on lichens living on trees. Judging by its colors this moth must be either noxious or its flavour leaves something to be desired. Are the toxins manufactured by the adult moth, or does it sequester them as a larva?

There are several species of Grammia with similar markings; I think this one is an Anna Tiger Moth (Grammia anna). Thus far I've been unable to find a theory or an explanation as to the reason for the strongly contrasting, albeit aesthetically pleasing, geometric patterns.

Do the contrasting reds and blues of the Squash Vine Borer (Melittia cucurbitae) mean it's toxic? Or is this moth meant to resemble a wasp like many other Clearwing Moths belonging to the family Sesiidae?

Larvae such as this White-marked Tussock Moth (Orgyia leucostigma) caterpillar are often more colorful than the adult moths. Hairs in themselves act as a deterrent to an insect being eaten, and of course the pretty colors aren't just for show – contact with the hairs of this caterpillar can cause an allergic reaction.

It would seem that the much more somber adult moth lacks the caterpillar's chemical defenses.

A pleasingly patterned Spotted Tussock Moth (Lophocampa maculata) perching on an Interrupted Fern frond.

One of the giants of the local moth world, the Polyphemus Moth (Antheraea polyphemus). The wingspan doesn't quite measure up to that of a Cecropia Moth, but it's close ...

The prominent purplish eyespots on the hindwings are thought to be a distraction display, startling a would-be predator for a vital fraction of a second and giving the moth a chance to escape.

The cryptic markings of a beautifully patterned Waved Sphinx (Ceratomia undulosa) serve well when it's perching on a tree trunk, but do little to hide it against the background of a brick wall. Not to mention its size ... with its robust cigar-shaped body and roughly 100 mm wingspan, the moth stands out like a sore thumb.

Look-alike, or almost look-alike, leps – the Eight-spotted Forester (Alypia octomaculata) ...

... and the White-spotted Sable Moth (Anania funebris). There are differences between the two species; the legs of the Eight-spotted Forester bear yellow tufts, and the patches on each side of the thorax of the White-spotted Sable Moth are yellow rather than white. Also (this is obvious when seeing the moths in the field, not a photograph) the wingspan of the Eight-spotted Forester is about 35 mm, that of the White-spotted Sable Moth is only around 20 mm.

So – how does all this decoration serve the ultimate goal of increasing the moths' chances of survival? Are the conspicuously spotted wings of these insects a coincidence, is one moth mimicking the other, or are both imitating a third distasteful insect species?

The wary, difficult to approach White-striped Black (Trichodezia albovittata) has a distinctive, butterfly-like manner of flight, and this little moth never seems to stop for a rest. Again, it strikes me as odd that this moth seems to attract attention to itself – despite its small size (the wingspan is roughly 20 mm) it certainly stands out when in flight and even continues to move its wings up and down, like a butterfly, when perching. What's the benefit or advantage of the bold markings?

Last but not least, a Geranium Plume Moth (Amblyptilia pica), easily mistaken for a piece of dried plant debris as it takes a rest on a thistle.

So much yet to learn about such a simple thing as the reason for the myriad variety of patterns and colors in a moth's wings! Biologists and scientists in general certainly have their work cut out for them in unlocking the mysteries of our natural world, and, as always, every answer will spawn a dozen new questions, but that's what makes science so much fun. In the meantime, areas of knowledge will remain hidden from our view – "eclipsed", figuratively speaking ...