Archive | September, 2012

I’m calling these potato monsters

21 Sep
Gall aphid colony in pecan leaf (Phylloxeridae: Phylloxera spp.)

Gall aphid colony in pecan leaf.

I wrote this post up back in the spring, then accidentally deleted it and was too disheartened to come back to it for months.  But these little guys are too cool to abandon forever.  The little yellow potato monsters in the photo above are pecan gall phylloxera, a relative of aphids and thrips.  They are exceedingly tiny.  So tiny that although I observed and curiously popped open the large pecan leaf galls many times while rearing my lunas, it wasn’t until I idly took a look under a scope one day that I even realized the little insects were there.

Open and closed pecan leaf galls with gall aphid colony (Phylloxeridae: Phylloxera).

Open and closed pecan leaf galls with gall phylloxera colony.

Pecan phylloxera have fascinating, complex life cycles.  These vary quite a bit between species, but I’ll share a general example, that of Phylloxera devastatrix, probably the most damaging pecan phylloxera.  Pecan phylloxera galls are started by “stem mothers,” who inject a toxin into the plant while feeding on young tissue.  This toxin stimulates the plant to grow a gall, gradually encasing the feeding insect over the course of several days.  Each stem mother then lays eggs in her gall, which develop and feed in relative safety.  In late summer, at the end of the gall’s life cycle, the galls split open, allowing winged asexual phylloxera to disperse.  They’re not done yet.

Close up of pecan gall aphids and eggs (Phylloxeridae: Phylloxera).

Close up of pecan gall phylloxera and eggs.

Not content with such a simplistic, multigenerational life cycle of barely three tiers, the asexual phylloxera find a good spot and lay some eggs.  Two different sizes, just to be more special.  The large eggs hatch into sexual females, and the small eggs into sexual males.  The phylloxera mate, and the mamas-to-be seek out a nice sheltered place…where they die.  This gives the eggs a nice, cozy refuge to ride out the winter–tucked up safe in mom’s dead body.  In the spring, the eggs hatch out of their mother and become stem mothers, which disperse to find young plant tissue and start new galls, beginning the beautiful cycle of life once again.

Damn, I love nature.

More pictures:

Gall aphids and eggs in an opened pecan leaf gall (Phylloxera spp.).

Gall phylloxera and eggs in an opened pecan leaf gall.

Pecan leaf gall aphid (Phylloxera sp.)

Close up of pecan leaf gall phylloxera.

Underside and mouthparts of pecan gall aphid.

Underside and mouthparts of pecan gall phylloxera.

Pecan gall aphid nymph and adults and eggs (Phylloxera)

Pecan gall phylloxera nymphs are exceedingly tiny.


Phylloxera gall on Pecan, TAMU

Pecan Phylloxera, Smith & O’Day

Pecan Phylloxera, OK State

Spiders raiding ant nest

3 Sep
Spider predating on Pogonomyrmex nest at night.

Spiders slip inside a sleeping harvester ant nest to prey on the worker ants.

Last week I had the pleasure of attending the new Ants of the Southwest course at the Southwest Research Station in Arizona, and I thought I’d jump right and share with you my favorite entomological encounter.  While black lighting in the desert we happened across a harvester ant nest that was being raided by dozens of small hungry spiders.  The spiders would slip inside the nest entrance individually and emerge some time later, dragging worker ant prey.   It was pretty impressive to watch, particularly as there was no evidence that the spiders’ raiding was provoking any kind of response from the colony.  Harvester ants (or “pogos,” from Pogonomyrmex) are a group of ants with a fairly vicious sting, and the workers dwarfed their tiny spider predators.

I’ve included more pictures as well as a video below, with bonus excited chattering commentary.

Spider entering Pogonomymex nest and killing workers.

A spider drags its harvester ant prey from the sleeping nest.

I don’t have an ID for the spider as of yet.  Several group of spiders are known to mimic ants, either to help them obtain prey or to help them avoid predators.  If these spiders don’t look like ants to you, it’s possible they may smell enough like ants to fool the colony.  Cosmophasis jumping spiders use this scent-disguise tactic to enter weaver ant nests and prey on workers and larvae.  Meanwhile certain spiders in the genus Masoncus take this a step further and live only inside harvester ant nests, where they prey on another nest symbiote, collembolans.

Spider feeding on its harvester ant prey.

A spider hangs from a grass blade, feeding on a harvester ant many times bigger than itself.


Thanks for the feedback here and over at Bugguide.  These spiders appear likely to be members of the family Theridiidae and the genus Euryopis.  Many members of this genus appear to be specialist predators of ants.  I poked around in the literature and there are a couple of papers about the species E. coki, a specialist predator of another species of harvester ants, Pogonomyrmex owyheei.  (I believe the harvester ants pictured above were P. maricopa.)  There were a number of similarities to the behavior I observed.  E. coki was observed to lurk outside nest entrances and ambush ant workers, first tacking down a leg with silk and then biting the ant.  When bushes or grasses were nearby the spiders employed a dangling feeding behavior (Porter and Eastman 1982).  Dale Ward has a great shot of a male Euryopis mating with a female spider near the nest entrance of P. rugosus.  Tetramorium’s Ants of Arizona page also has some great shots and info.  I haven’t been able to find any literature on thespiders actually entering the ant nests, though.