This Week in Anting 09/16/2017

 This week I got to try PawPaws for the first time ever and Lasius neoniger flew! 

Asimina triloba is the northern most member of the custard apple family which is largely tropical. This is the only species native to the United States and one of the few host plants to the Zebra Swallowtail Butterfly. The flowers are pollinated by small vinegar flies and are supposed to require a second cultivar or genetically different tree of the same species in order to produce fruit.... but this is the only tree in my yard and probably the only tree in the whole county. It would seem this cultivar is semi-self fertile. The tree is roughly 12' tall and produced 12 sizable fruits though not on every branch that flowered. Presumably had there been a genetically different tree nearby it would have made even more fruit. (It's either 'Sunflower' or 'Pennsylvania Gold')

The smell is amazing when ripe or slightly damaged. The fruits perfume the air with a fragrance that leaves one assuming some sort of Banana and Orange factory has exploded somewhere. It's very potent and alerts the homeowners, hikers, and wildlife that the fruit is ready. 

The inside texture is somewhat gooey verging on vanilla pudding except for the fairly large and flat seeds with are like skipping stones or pebbles. The taste of a slightly unripe one is that of bananas with hints of cantaloupe (or musk melon as it's known in most of the world). A fully ripe one tastes more like a really sweet banana with a candy-like quality to them. It's a shame this fruit has such a short shelf life of about a day and a half because that's been the main reason it hasn't become main stream. (When they are for sale they can sometimes go for $15 a pound!)

 Fruit such as this is intended to be eaten by animals and carried away from the tree in the wild. If it just falls to the ground though it falls on other creatures to then remove the fruit and free the seeds within. Fungus and mold will do the job otherwise but may also destroy the seeds within.

 Members of what must be a very happy Prenolepis imparis colony spent the day cutting up the fruit and hauling it home after most of the workers had engorged themselves on it.
 

 A fairly decent anatomy pic showing off the acidopore, a slightly tuft of hairs at the tip of the gaster/abdomen. This is a key trait when identifying ants in the subfamily Formicinae and a conclusive way to tell them apart from members of Dolichoderinae.

 Another good anatomy shot. Here the tiny waist segment is clearly visible separating the gaster from the mesosoma.

 Brachymyrmex dipilis was also flying that day. This is one of the smallest ants in the U.S.

Lasius neoniger Nuptial Flight

My friend out in Indiana found a Lasius neoniger nuptial flight happening. They're called the Labor Day Ant because their mating season normally takes place around the same time. This video was taken two days ago so they're still finishing up. This is a common grassland ant found all over North America.


Queens in this genus will sometimes band together during the founding stage to better ensure a successful colony. Workers however, will only tolerate one queen in the nest so after 4 weeks or so they'll slowly start killing off the submissive ones. The advantage to a single queened colony is order. Workers will be better able to fatten up the reproductives produced from one queen as opposed to a multi queen nest which won't be able to feed their reproductives anywhere as well.

Lasius Ants in North America

Lasius is such a diverse genus of ants. These are small/medium sized ants about 3mm to 6mm. "Ants of North America," lists 33 species in back of the book. Species in this genus have been divided into 4 groups, niger, flavus, umbratus, and claviger. The niger group (pronounced nyjer!) boasts big healthy looking queens that have enough stored food to start colonies on their own. In the ant world this isn't saying much, queens in assorted ant genera do it all the time. But in the Lasius group it's worth pointing out.


Here is a Lasius (niger) neoniger queen with two darkly colored workers. Queens in the flavus group are also capable of starting colonies on their own. Species in the flavus group tend to be smaller and more orange/brown in color. Workers in the flavus group also tend to be orange in color.

In order to talk about the umbratus and claviger groups one has to learn how colonies are founded first. Overpopulation and limited nesting space has driven queen ants to sometimes band together and tolerate one another's presence until the first workers are born. This saves the queen ant the trouble of killing the other 40 or so queen ants who've all decided to start a colony under the same rock. The result is a massive colony that suddenly appears some weeks later.

But there is an issue here. With so many queen ants in the colony, the next generation of reproductives won't have enough food to start colonies of their own. So after the first workers are born an internal power struggle occurs. Workers will slowly kill off queen ants in the colony. As they begin foraging other small colonies might be discovered. These are either killed immediately or integrated into the new colony. Eventually though all but one queen is left the new colony and she becomes the primary egg layer. (Occasionally the last queen standing may die of her injuries too.)

This system has lead to a number of evolutions. Firstly queens that band together tend to be more successful becuase they produce more workers then the starting colonies around them and are better able to deal with stronger colonies that have been around longer. There are two flaws though.


1) Queens aren't picky about what species of Lasius queen they start a nest with. Pictured above are two queens of Lasius neoniger and one queen of Lasius alienus stating a colony. The L. neoniger queens tend to be much better parents and care for the eggs when disturbed.

2) The first workers of the colony don't always choose the strongest queen to be the primary egg layer. Simply saving your energy and appearing to be the best queen is more important than actually being the best choice. It's this that umbratus and claviger species take advantage of.


Both claviger and umbratus queens tend to be slimmer, they don't have as much stored food in their abdomen, and they require an existing colony of Lasius to start a nest. Queens in the claviger and umbratus groups are social parasites of species in the niger group.

Having to successfully sneak into a colony and replace it's queen without the workers getting wise is a tricky business. Over millions of years these social parasites have learned a number of tricks. Playing dead to be brought in the nest as food, sneaking in the nest before the workers have started favoring and killing queens, spraying citronella odors to confuse workers, and out right badging in the colony entrance are just a few methods observed over the years. Even with such a variety of methods to employ success is still very low.


Ants rarely give up though and social parasites also employ the oldest trick in the ant book, overwhelming numbers. Social Parasitic species of Lasius out number their hosts 10 to 1. Their nuptial flights are 10 times bigger. Every year a colony of Lasius claviger completely covers my front steps in flying ants.


Easily a couple thousand queens pour out of each colony and continue to do so for day. Queens land after mating and begin their task of taking over a colony. Once completed, the host workers will take care of the parasitic queen's brood and slowly the colony changes it's colors.




In a matter of 12 or so weeks the entire workforce is now that of parasitic species.



The host species simply dies out. Though the queens need assistance to start a colony, her workers are more then capable of taking it from here.


Underground root aphids prevent the need for foraging on the surface. Umbratus, claviger (and I want to say flavus but I'm not certain,) forage almost exclusively underground. They emerge above ground only during their mating season.


The honeydew from the aphids is nutritious enough to feed the whole colony. The occasional dead worm also makes it's way into the mix though.


Cocoons are incubated near the surface under stones or logs.

The only real difference between umbratus and claviger group species is that claviger is known for producing the citronella odor. Gardeners are probably most familiar with it. Accidentally digging up part of a colony fills the air with a sweet lemony scent.