This Week in Anting 10/20/2017

What might be the last This Week in Anting of the year.

This Week in Anting (Myrmecochory)

This week Woodland Poppies and Bloodroot went to seed. Both plants have elaiosome on their seeds which entice ants into dispersing them.

Twinleaf also went to seed but none of my plants flowered at the same time as one another. Presumably the lack of crosspollination means the packets of elaiosome on the seeds are smaller, and they're already pretty tiny on these plants as it is. Pictured above is Crematogaster cerasi which isn't strong enough to physically lift the seeds. Even the seeds that fell out of the pod naturally from the wind blowing it around were practically unmoved.

So the focus was on the Bloodroot and the Woodland Poppy. Both have great big packets of elaiosome on their seeds. I would love to include Twinleaf one year but they're tricky; seedpods can seem ripe but the seeds inside might still be soft.

Bloodroot seeds are about the same size as Twinleaf, and the packets of elaiosome are huge by comparison.

Woodland Poppy seeds are smaller but also have tons of elaiosome on them, though they look different. Actually the seeds to this pod are just shy from being ripe as they're normally black colored, but these should be dark enough that they'll still grow.

The two main ant species attracted are the Odorous House Ant, Tapinoma sessile, and....

... Aphaenogaster rudis. This ant for the most part doesn't have a common name. In "A Field Guide to the Ants of New England" they're referred to as "The Rough Aphaenogaster" which refers to a rough spot on the thorax that set it apart from other Aphaenogaster. The problem here though is the genus name is in the common name so why bother? Also A. rudis has been found to be a HUGE species complex! I forget the exact number but I recall a study saying there was something like 8 or 16 nearly identical-looking species that all fall under the A. rudis blanket. Each one has a different number of chromosome in their DNA so you actually have to look at their blood to tell them apart. I don't have access to that kind of tech so for convenient sake they're all A. rudis, and to be honest they're all pretty similar to one another. I've found a few colonies before that have multiple queens and others that only have just one, some colonies seem to divide, but all pretty much nest in forests with colonies of ~2,000 ants.

Tapinoma sessile are either incapable or unwilling to transport Bloodroot seeds.

The seeds overall are too large and bulky for them to lift so they spent the whole time just nibbling at the elaiosome.

They started to bite pieces off and carrying them back to the nest bit by bit. At no point did they actually move the seeds other than to accidentally jostle one or two of them free of the pod.

Aphaenogaster rudis on the other hand was more than happy to haul the seeds off.

They would latch hold of the elaiosome and drag them back to the nest that way.

With Woodland Poppy, I was amazed to see Tapinoma sessile workers actually carrying them back to the nest. Most of their time was spent on removing the elaiosome from the seeds within the pod but several of the workers actually did disperse them... the colony is nesting in a soliar light but they're still dispersing them.
 

This is a native ant species so it's not too surprising to see them dispersing a native plant species but there is still a problem. The Odorous House Ant is often the little black ant seen running around your bathroom and kitchen counter. They nest opportunistically in mulch, under tree bark, and in man made structures. So they're not the best ant to be dispersing seeds because they can end up in the walls of your home, in foundation bricks, or under loose bark, but also in the mulch of your garden, and in flower pots. So it's the flip of the coin as to whether they end up in a spot they can grow. 

Aphaenogaster rudis is better at the task. 

 They're generalist scavengers more in the habit of bringing food items back to the nest.

 They nest under logs, in leaf litter, or along clumps of grass.

At no point during my observations did I witness any try to remove the elaiosome from the seeds outside of the nest. Actually shortly after bringing them into the nest the seeds were quickly discarded out to the colony's midden (trash) pile which was hidden among leaf litter.

Midden piles are where ants put their garbage. Old insect carcasses, dead workers, spent cocoons, general roughage and things to be discarded all get piled up here. In deserts of the South West they're very noticeable around ant nests but here in the forests of the North Eastern United States they're often hidden under leaf litter.

Overall were it not for the ants dispersing these seeds they wouldn't have gotten very far. New plants would try to germinate just inches away from the old ones and the patch would move at a snails pace and only on the rarest of occasions would they travel up hill. Thanks to the ants carrying the seeds off, even if they're dropped or discarded shortly after, new populations of these plants can spring up to 24' away, potentially more if colonies fight over them or raid the midden piles of other colonies they often do for dead ants.    

Other ants that also showed:
Prenolepis imparis - single worker that did not recruit other nest mates.
Nylanderia flavipes - even smaller than Tapinoma sessile in size. Barely able to remove elaiosome. did not disperse seeds.
Temnothorax curvispinosus - even smaller than Nylanderia flavipes. Incapable of recruiting nest mates as they don't use chemical trails.

Caterpillar on Sourwood Tree with Ants

It's always exciting when Ants, Bees, Butterflies, and Nature can all come together. This is the former long winded title of this blog, which I've since changed to Biodiverse Gardens. 

So two years ago I planted a Sourwood tree as a nectar plant for my Honeybees. They've yet to find it this year but really it's still just a sapling barely 6' tall. This is one of the prized nectar flows among beekeepers because it produced great tasting honey. Unfortunately it's a rather uncommon landscaping tree in my area and doesn't occur in wild forests here, so for the most part my planting this tree is like adding a drop in the bucket to my overall honey harvest. Still though I'd rather plant a world class honey tree over the more commonly sold plants offered at local garden centers.  


Earlier today I discovered what looks like one of the Blues or Azure Caterpillars feeding on the flowers. This is odd for a few reasons: I live in New Jersey and Sourwoods don't grow here wildly, so it's unlikely to see this kind of relationship so far outside of the tree's native range.

I have heard of Zebra Swallowtails finding groves of Paw Paws here in NJ so maybe something similar has happened, but more likely one of the species that was already here has made the jump to a new host plant, or is using one that they would normally use when they occur farther south.

Also odd, is that no one seems to have ever reported this type of caterpillar on Sourwoods before. Or maybe I'm just not looking hard enough but all the listings for Sourwood in "Caterpillars of Eastern North America" don't look correct for this species.

Another bit of intrigue, prior to the caterpillars showing up, the ants, Tapinoma sessile, were stealing the nectar from the flowers. But now that the caterpillars (there's just 2 of them that I counted,)  have shown up and started eating the flowers, the ants have changed their behavior. Now instead of stealing from the flowers they're tending the caterpillars which are eating the flowers. 

This probably doesn't benefit the tree at all. Flowers that have been nectar robbed can still produce seed, whereas flowers that have been eaten won't develop into anything. The only benefit as far as I can tell is that the ants have stopped nectar robbing the whole tree and are now just going to the section where the caterpillars are found. So sacrificing a few flowers might benefit the tree overall.

When I started my native plant garden, this was one of the behaviors I'd hoped to attract into my yard. Ideally I pictured it happening in a field of Wild Lupins saving an endangered species of Blue but this also works. What eventually happens is the caterpillar drops to the ground and is taken into an ant nest where it then pupates... some species change their diet to eating the ant brood before pupating but the ants don't care at that point. These sorts of caterpillars, along with producing nectar and being treated like cattle, also make noises that mimic the sounds a queen ant makes when she wants to be tended. Ants themselves are also more than happy to eat their own eggs or feed their eggs to developing brood more worthy of the nutrients so this isn't unant-like behavior. They're safe in the nest until the following spring, when they must emerge a butterfly and quickly get out of the next to spread their wings.