The lion's share of the aphid

A few weeks ago, while I was on a trip to Arizona, I took a walk in the desert.  (I did not make much progress as far as walking was concerned, though.)  There were many flowers blooming along the sides of the trail, so I zigzagged  from one flower to the next, checking for crab spiders or any other visitors (but really hoping for crab spiders). 

Brittlebush (Encelia farinosa) flowers and one of the several crab spiders that I found.

It was not long before my diligence was rewarded by my discovery of a very small crab spider.  After that, I checked each flower even more intensely and in the end found several small crab spiders, some with even smaller prey. 

A juvenile crap spider (Mecaphesa sp.) eating what looks like a thrips.

For example, the spider above is eating a tiny insect that appears to be a thrips.  Meanwhile, the remains of another crab spider's meal can be seen in the bottom left corner of the picture below (it is probably a tiny fly or bee).

This crab spider had already finished its meal (if you look closely, you can see what was left of it).

In my search for the spiders, I also encountered quite a few other visitors to the flowers, including another successful predator.  This predator was a lacewing larva that I caught in the act of living up to its name 'aphid lion'.

A lacewing larva, a.k.a. an aphid lion, with a captured aphid.

Ladies in waiting

A little over two weeks ago, I found a cluster of bright yellow eggs underneath a linden (Tilia sp.) leaf.

A cluster of lady beetle eggs on the underside of a linden leaf.

Although I did not need to wait for the eggs to hatch to know what was inside -- developing lady beetle larvae -- I hoped to see the larvae before they dispersed.  Therefore, I made a mental note of where the leaf was and occasionally checked on the eggs.  Finally, after two weeks, there was a change.

The lady beetles shortly after hatching.

The lady beetle larvae had emerged from their eggs.  Soon, they would spread out in search of food.  Checking the surrounding leaves, I saw that the lady beetle larvae would not have to go far to find a plentiful supply of aphids.  However, they would have competitors, as more batches of lady beetle larvae were hatching nearby.

A linden aphid (Eucallipterus tiliae) on a nearby leaf.

And then there were none

I periodically check on the aphids on the pine tree and have been keeping track of one colony in particular.  In early November, this colony was growing rapidly.  However, after reaching a peak of nine aphids, the colony went into decline.  It lost one then another of its three adults, leaving just one adult surrounded by a few juveniles.

The dwindling colony of aphids.

A few days later, all the aphids of the colony were gone.  They may have succumbed to the cold and wind, or perhaps to something even more sinister. 

A seven-spotted ladybug (Coccinella septempunctata) on the pine tree.

Although I haven't seen any ladybugs (such as the one pictured above) on the pine tree for the last few weeks, I have caught glimpses of a few camera-shy spiders on the branches.  I also found one aphid that was missing a leg, perhaps as a result of being attacked by something.

An aphid missing its hind right leg.

Saved for a rainy day

It has been cold and rainy for several days, making it difficult to see much of interest in the backyard.  Even when I dared to take my camera outside during a slight break in the weather, my potential subjects were still in hiding.  After some searching, I did find several insects sheltered in various spots around the yard.  The fact that they were not engaged in any interesting activities was somewhat compensated for by their being much more obliging than usual and staying very still as I moved the camera close.

A fly shelters from the rain beneath some flower buds.

Although I did not find much outside, I did discover some unedited videos on my computer.  The video below is from a time when the air was full of insects, rather than water.  I took it to illustrate the surprising number of woolly aphids flying around in early October.  If you look closely at the cotoneaster branches, you can also see the shimmering of spider webs (where many of the aphids ended up). 

* To see this video in high definition (1080p), you may need to (1) click "YouTube" to watch on the YouTube website and (2) change the settings at the bottom of the video screen.

Clones in a row

Pine needles are tough and don't seem like they should be very appetizing.  Nevertheless, after my close encounter with a western conifer seed bug, I decided to start paying more attention to the pine tree in the backyard.  In one of my searches, I found a needle that had been colonized by aphids.

Five aphids on a pine needle.

These aphids can pierce through the pine needle to feed on the sap.  Despite the apparent difficulty of feeding on a needle, they seem to be doing quite well.  When I first found this group of aphids, there were five of them.  When I went back to check three days later, they had already produced three more clonal daughters!

Eight aphids on the pine needle.

New arrivals

This weekend, I went in search of the source of the woolly alder aphids (Paraprociphilus tessellatus) that have been swarming my neighborhood.  When on tree branches, these aphids form white, woolly masses that should be easy to spot.  I don't have their host plants (alders and maples) in my yard, but I thought some of those trees must be nearby.  I checked the alders in a nearby park, but their branches appeared clean.  If it hadn't been windy, I might have gotten a clue about where to look from the density of the aphid cloud.  As it was, I didn't see any aphids flying at all.

Wherever they had come from, the woolly alder aphids were still all over my backyard.  Some were sitting on foliage, presumably sheltering from the wind; quite a few others had been caught in spider webs.  While looking for the woolly aphids, I also discovered several more typical aphids -- ones that might be content with the plant selection in my yard.

A winged aphid on a morning glory leaf.

A winged aphid surrounded by her juvenile offspring on a rose leaf.

For much of the year, aphids reproduce asexually.  Without mating, the females can give birth to many live daughters, which are soon ready to produce their own daughters.  Therefore, a single aphid can quickly generate a large population. 

However, there is little chance that these new aphids will pose a threat to the plants in my backyard.  Starting tomorrow night, we are expected to have a series of hard freezes.  Even if the aphids survive the frost, there won't be much more damage that can be done to the plants this fall.

Mystery solved

When I came home yesterday evening, I noticed that the fluffy, white insects were not limited to the backyard.  They were also drifting around in front of the house, as well as up and down the street.  I decided to make another effort to identify them.  I was able to scoop several out of the air with my hand, and I captured one in a glass jar for closer inspection.  Going through the insect key from the beginning, I found that what I had was a woolly aphid (Aphididae, subfamily Eriosomatinae). 

A woolly aphid migrating to a new host plant.  For scale: this aphid is about 3mm long.

These aphids alternate between feeding on alders and silver maples.  While on one host, they form dense colonies of wingless clones.  Then, when it is time to migrate to the next host, they produce winged offspring like the one pictured above.

Paying for protection

Generally, when I inspect a plant in the garden, I do not want to find aphids on it.  Aphids puncture the cells that transport nutrients up and down a plant's stem and then drink the sugar-rich sap that leaks out.  Since aphids reproduce rapidly, they can inflict serious damage to the host plant if left uncontrolled.  Therefore, I almost always remove the aphids as soon as I can.

However, I make an exception when the aphids are accompanied by ants.  The opportunity to observe the ants trumps (at least temporarily) my concern for the plant's welfare.  Instead of just eating the aphids, some ant species will tend the aphids like livestock.  When the ants touch the aphids with their antennae, the aphids excrete a sugary honeydew that is collected by the ants.  The ants aggressively defend this valuable resource, thereby protecting the aphids from attacks by their natural enemies -- or, in the case of this video, a  dry grass stem. 

* To see this video in high definition (1080p), you may need to (1) click "YouTube" to watch on the YouTube website and (2) change the settings at the bottom of the video screen.