#1236-1239 - a Roadside Ecosystem
#1236 - Syrphid Maggot - Aphid-lion
Back in 2015, I pulled up at a job, looked down at the weeds beside the driveway, and discovered an entire ecosystem of parasites, predators, other parasites, and pathogens. And I only noticed the pathogen this evening. Which only goes to prove just how behind I am in posting the species I’ve actually managed to ID.
The plants were Common Sowthistle, Sonchus oleraceus, and it was heavily infested with Brown Sowthistle AphidsUroleucon sonchi , so I knelt down in the hope of finding anybody taking advantage of this - and I did. This hoverfly larvae is gorging her way through the infestation, something many of the more common hoverflies do as maggots.
#1237 - Uroleucon sonchi - Brown Sowthistle Aphid
A common aphid, at least on Sowthistles (Sonchus sp.) and allied plants, like lettuce. Occasionally, they’re a serious pest over east, but so far that doesn’t seem to be the case in Western Australia. Of course, there’s also the risk of them transmitting plant viruses into the crops, but I don’t know if this particular species is a known vector.
This is a large genus with 226 species distributed worldwide associated almost entirely with the daisys (Asteraceae) and bellflowers (Campanulaceae) families.Uroleucon aphids are very fussy about their hosts - some are found on on a single species of plant. They do not host alternate.
Aphids can reproduce asexually, which is great for starting new infestations and building up the numbers rapidly. These ones, on the other hand, usually reproduce sexually, and overwinter as eggs. Here in Australia that probably means they breed all year round. Great snack for hungry hoverfly maggots or ladybirds, of course, and I’m sure their are tiny parasitic wasps that will go after them too.
Some species of Aphid are farmed by ants, for the honeydew they secrete - that’s not the case with Uroleucon aphids, usually.
#1238 - Diplazon laetatorius - Hoverfly Parasitoid
After photographing the hoverfly maggots and their prey the Brown Sowthistle Aphids, I notice somebody else at the dinner table - a small wasp busily exploring the Sowthistles. I was very satisfied with this, since it’s the Ichneumonid wasp Diplazon laetatorius. But it’s not parasitic on the aphids - it’s hunting for hoverfly larvae.
#1239 - Miyagia pseudosphaeria - Sonchus Rust
And then, tonight, as I was getting these photos together to post on my blog, I noticed that many of the Sowthistle leaves had little yellow pimples on them, surrounded by dark pinkish rings - it soon figured out that it’s a another specialist, the Sonchus Rust Fungus (Miyagia pseudosphaeria).
The fungus was first noticed in Australia 20 years ago or so, but has no real effect at controlling the weed. Nor are the aphids, and their predator has its own problems, in the form of the wasp. True, it all reaches a balance eventually, but that balance is an invasive weed occupying habitat better reserved for Australian native plants, if you can find any that will survive beside driveways.