Andrea has posted other stories & pix about arthropods! See also:
Last week of June, 2007: Six photographs for Bug-Eyed
Time for a break from all the serious posts. I finally got some new batteries for my D-SLR, so between [much-needed] rain showers I snapped some insect pix. By “bug-eyed” I’m referring to the ability to spot little insects amidst masses of flora. For example, here’s a frothy mass of fennel plants growing in the garden. There are several caterpillars and some eggs in here, but you probably can’t see them at this level of resolution.
By “bug-eyed” I’m referring to the ability to spot little insects amidst masses of flora. For example, here’s a frothy mass of fennel plants growing in the garden. There are several caterpillars and some eggs in here, but you probably can’t see them at this level of resolution …
Okay, we’ve closed in on one. You’ll first spot the larger of the caterpillars. These are young black swallowtail butterflies (Lepidoptera: Papilionidae Papilio polyxenes asterius). These particular caterpillars (butterfly larvae) undergo several changes in coloration as they grow. The larger caterpillars are banded in green, yellow and black. This only sounds outrageously flashy; in reality, they easily blend into all the light and dark bands of the foliage. This one is one of the middle size growth stages, about 2 centimeters long (3/4 inch). Like other insects, caterpillars must shed their older, too-small cuticle when they grow. This one appears to have just done so, and you can see the rumpled-up empty remnant of its previous “skin” behind it, like a striped unitard discarded on the bedroom floor. (Kids everywhere are messy.)
Younger, smaller caterpillars of black swallowtails don’t look much like their older siblings. They are primarily brown, with a white saddle across the middle, and are covered in bristly orange spikes. Only a few millimeters long, they look like nothing so much as a bird dropping, which is a good camouflage when birds are one of your prime enemies! As another defense, this particular species can also evert a Y-shaped organ from its head called an osmeterium, which exudes a nasty smell not unlike vomit.
The eggs of these butterflies are much smaller, no more than one millimeter in size. The females will lay them singly on any of a related family of plants (Umbelliferae), including fennel, dill, parsley, carrots and so on. These insects are oligophagous, meaning they will only eat a few species of plants. Because of this, the caterpillars bear the common name of “parsley worm” (even though they are not really worms). My local butterflies seem to prefer laying eggs on the volunteer fennel plants instead of the dill or parsley. Caterpillars also have preferences. Once one gets used to eating a particular host plant, it doesn’t want to switch, much like some people who prefer to drink a particular brand of cola. Other species of insects will also exhibit this “induced preference”. (Kids everywhere are picky.)
This butterfly is also sexually dimorphic, meaning that the males and females look different. The adults are large butterflies, with a wingspan of 7-8 centimeters (3 inches), with thin “tails” trailing off their hindwings. They are mostly black with a single row of small yellow spots at the margins of the forewings (those by the head) and the hindwings (those by the back end). The males have a row of large yellow spots near the margins of the forewings and hindwings, and the females are notable for having a row of blue spots near the margin of the hindwing. There can be two or three generations per year, and this species overwinters in chrysalis, the pupation stage when the caterpillar transforms into butterfly. Once they emerge as adults, they feed on flower nectar, and go out in search of mates.
Second week of June, 2007: Three photographs for The Feeling’s Mutual
I’d hoped to take some pix of the black swallowtail caterpillars on the fennel, but alas, they are no more to be found. Instead, I found that the volunteer sunflowers are hosting several new species of insects that I’d not yet seen in the garden. Except somebody forgot to tell the lacebugs, treehoppers, and ambrosia aphids that they’re on the wrong plants.
When I checked out the exact species of these recent immigrants in my ID books, I was annoyed to see that the allergenic devil, the giant ragweed (Asteraceae: Ambrosia trifida) is supposed to be their host plant. Well, sunflowers are in the same giant family of plants (Asteraceae: Helianthus annuus). But of course the insects couldn’t be taking down those annoying weeds I keep yanking, they have to be infesting the volunteers I like! Such is garden life.
So out in the front yard the sunflower has the lace bugs (Hemiptera: Tingidae Corythucha marmorata), essentially miniature (3mm) lace doilies that like to scuttle about and suck plant sap, plus the brown ambrosia aphids (Homoptera: Aphididae Macrosiphum ambrosiae) which I would describe more as maroon than as brown. As aphids go, they are big, not much longer than the lace bugs, but seem bigger because of their long appendages. If you’ve ever wondered just how the critters manage to suddenly infest your garden, when conditions get too cramped the aphids will produce “alate” (winged) offspring, and once those find a suitable host plant, they in turn will produce offspring without wings.
Out in the back yard, the sunflower is supporting a mutualistic association of large ants (5 mm !), along with the giant ragweed treehoppers (Homoptera: Membracidae Entylia bactriana) which tiptoe about armored in delightfully funky pronotums. I think the ants are the Allegheny mound ant (Hymenoptera: Formicidae Formica exsectoides), which is fond of sap-sucking insects (such as aphids and treehoppers), for the purpose of um, consuming the “honeydew” they excrete. Plant sap is high in sugars, but low in Nitrogen, which all animals need to make amino acids for proteins, nucleic acids and whatnot. So the sucking insects filter out the goodies and pass a lot of sugary water (the “honeydew”) out the back end. Ants will stroke their sedentary food producers with their antennae as a prompt, and then consume this honedew. The ants will also protect their livestock from predators (most Homoptera are not known for their maternal care), so it’s a win-win situation for both species, or mutualism.
Unlike antimacassars, lacebugs make messes
an alate (winged) brown ambroisia aphid with her daughters
ant and its treehopper livestock with her offspring
Fifth week of May, 2007: Five photographs for CRUSH! KILL! DESTROY!
Several days ago I noticed that I had a couple of green peach aphids on some cabbagey plants. Did I pull out the insecticide? No, I waited a few days and returned with my camera to witness the inevitable carnage, because aphids are the McDinners of a number of beneficial predators, not just ladybird beetles, but also syrphid flies, lacewings, and most fearsome of all, the parasitoids!
Green peach aphids (Homoptera: Aphididae Myzus persicae) are polyphagous, meaning that they eat a number of unrelated things. Well, one never has “an” aphid; like the Tribbles of Star Trek fame, they are born pregnant, with their grand-daughters, no less (this virgin-birth process is known as parthenogenesis). Sure enough, in a couple of days there was a rollicking infestation of aphids. Aphids suck. They are sap-sucking insects, and not only cause primary damage by wilting the plants, but can also cause secondary harm because they are disease vectors. And of course, once an aphid finds a suitable host plant, she pops out lots of daughters who grow up in a few days to pop out daughters of their own, and …
It’s hard to photograph predators (beyond the usual insect macrophotography issues of sudden wind, abrupt cloudiness confounding the lighting needs from multiple extension tubes, and the photographer’s natural manual shakiness), because they are normally on the prowl, and because any self-respecting aphid predator knows that their prey likes to hide on the undersides of leaves.
The home team defenders are mostly larvae, and like teenagers ravaging a pizza buffet, they can eat a LOT. Another distinguishing factor of larvae is that they don’t look anything like the adults, so are not easily recognised as being the “good guys”. Included are the ladybird beetle larva (Coleoptera: Coccinellidae), the green lacewing larva (Neuroptera: Chrysopidae), and the syrphid fly larvae (Diptera: Syrphidae). Although the larvae are predators, sometimes the adults are not; the adult syrphid flies are pollen and nectar feeders, and thus fill the rôle of minor pollinators.
Ordinary predators just roam around and chow down on herds of aphids. Parasitoids are a whole ‘nother form of terror. The female wasp lays an egg either outside the prey (ectoparasitic) or inside the prey (endoparasitic). The wasp larvae then consume their hosts, although generally do so in a manner that allows the infested host to keep feeding and living long enough to support the maturity of the wasp larva. There are a number of different types of parasitoid wasps, including Ichneumonidae, Braconidae and other families. They are by necessity very tiny wasps, and not the sort one needs to fear being stung by. In the case of aphids, the wasp (Hymenoptera: Aphidiidae) lays an egg inside an aphid, and over a few days the aphid’s body becomes bloated and hardened. The mature wasp then emerges by cutting a circular escape hatch in the back of the aphid host. It’s simultaneously gruesome and fascinating. The sex lives of parasitoids are even more bizarre, but that’s a story for another day.
Lacewing larva on the hunt (that’s the skinny pink thing on the left of the main leaf vein)
Adult Syrphid fly feeding on nectar
Syprhid larva (that’s the green, sluggy thing) galumphing around, hunting aphids
Ladybird beetle larva chowing down on green peach aphid
Mummy of a pea aphid after wasp has emerged from round “escape hatch”
Fourth week of May, 2007: Three photographs for Penstemons with Bees and Butterflies.
The current popular nectar source is the Beardtongue (Scrophulariaceae: Penstemon digitalis ‘Husker’s Red’), which is being heavily visited by the Carpenter bees (Apidae: Xylocopa virginica) and the Red Admiral butterflies (Nymphalidae: Vanessa atalanta). Carpenter bees can be distinguished from bumblebees by their shiny dark abdomens (they look like they’re wearing brand-new indigo-blue carpenter jeans).
Regal Fritillaries (yes, in copula)
Zebra Swallowtail (and a Skipper)
Argiope Spider, the estimable “Ms Boots”
Carolina Mantis “Mildred” on my Mac laptop
Ladybeetle larva chowing down on potato aphids
A sweat bee