Life of a carpenter ant

Carpenter ant pupa cocoon and first instar larvae.

Ants, like butterflies, are holometabolous and go through complete metamorphosis with an egg, a larva (~caterpillar), a pupa (~chrysalis/cocoon), and adult ant (~butterfly).  In ants, the larvae resemble small white grubs and cannot move by themselves–they are fed and tended by the worker ants.

Carpenter ant first instar larvae viewed under magnification.

The larvae are covered in fine hairs which help them stick together in clumps, making it easier for adult workers to move and tend them.  In fire ants, these hairs also help with rafting behavior, because they can trap a layer of oxygen around the larvae, helping them breathe and making them extra buoyant.  Rafting fire ant colonies use their babies as tiny floatation devices.  Please take a moment to consider the wonder of nature.

As they grow, the larvae molt several times, and each growth stage is referred to as an instar.  The larvae pictured above are extremely tiny because they are first instar larvae, having only recently hatched.

A pupating carpenter ant larva after spinning her cocoon.

When the larvae are old enough they prepare to metamorphose into adults.  Some ants, like these carpenter ants, spin themselves into cocoons to pupate, while others, like fire ants, leave their pupae exposed.  Above, you can see an opened cocoon that contains a larvae that has not yet molted into its pupal form.

Additional fun fact: ant larvae have a closed digestive tract (I assume to prevent them from making a mess all over the colony.  It’s like the ant equivalent of diapers.). They poop for the first time when they molt into pupae.  Best line from a paper ever:  “…the larva defecates for the first time…. Workers help out.” (Taber, 2000).  This is also the least appealing job description.

A carpenter ant pupa in her opened cocoon.

While the job of the larva is eating and growing, the job of the pupa is developing–reorganizing its system into an adult ant.  Ant pupa look basically like unmoving, pale adult ants, darkening up right before their final molt to adulthood.  The newly molted ants are still fairly pale and soft-bodied.  They are referred to as “callows.”  Their exoskeleton darkens as it hardens, until they are prepared to go about the daily business of an adult worker ant.

Adult carpenter ant worker.

PS:  Here is a cool video of a queen ant helping a pupa shed its old larval skin.

How to Build a Bunch of Different Formicaria

Since my “Ant Farms: How to Build Your Own Formicarium” page is one of my most visited articles, I’ve created a page to compile some different ant rearing/formicaria designs that I have seen or used.

Please check it out!

Acrobat ants in a flat plaster nest.

Carpenter ants checking out air holes at the top of a colony.

Monomorium ants with a tube nest.

Rover ants and queen with brood in plaster nest.

See more at:

Ant Farms: More formicaria designs

and see also:

Ant Farms: How to Build Your Own Formicarium

Techniques

Queen Ants – Founding a new colony

A foundress carpenter ant queen (Camponotus) tends her clutch of eggs, with her dropped wings visible in the foreground.

Lots of pictures of queen ants today.  While the huge diversity of ant species have developed numerous methods for founding new colonies, a few strategies are fairly widespread in the ant world.  After a nuptial flight, in which winged sexual male and female ants mate,a future queen faces the harrowing challenge of founding a new colony.  With her ovipositor specialized for egg-laying she cannot even sting or spray venom.  She has only her jaws to defend her and she is heavy-bodied and clumsy.  Mortality is high–one reason ant colonies pump out vast flocks of winged alates.  Dropping to the ground the new queen searches diligently for a nest site, shedding or pulling off her now useless wings so that she can burrow or explore small crevices more easily.  The energy from her atrophying wing muscles will be used to help feed her and her developing brood.

A foundress carpenter ant queen stands guard over her eggs after being disturbed.

Unless she manages to join an existing nest (some ant species such as fire ants will accept additional queens into established colonies) or co-founds with a small group of other queens (in which case surplus queens may later fight or be executed by workers) she will be alone until she manages to raise her clutch of eggs through the helpless larval and pupal stages and into small adult workers.  In some species queen ants take on the risky task of foraging for food, but in many species queens practice claustral founding, closing themselves away into small nest chambers until the first workers eclose, relying entirely on the resources stored in their bodies to provision them.

A cloistered fire ant foundress (Solenopsis invicta) with her brood.

During this time, queens carefully tend their precious brood, feeding them via  salivary secretions or trophallaxis (regurgitation) and grooming them to prevent mold or fungal growth.  Fire ant queens lay trophic (feeding) eggs, which they eat and then regurgitate to the larvae.

A foundress fire ant queen in a test tube tends her first larvae and pupae.

The first workers pupate prematurely, and eclose as unusually tiny adult ants, called minims or nanites.  The pale, callow workers slowly darken and gain mobility as their exoskeletons harden.  Driven by hunger and instinct, these tiny workers open up the colony and venture carefully forth for the first foraging expeditions of the colony. (Other tactics may also come into play–fire ant minims practice brood raiding, where they steal developing larvae and pupae from nearby colonies to enlarge their own labor force.)  Later workers, tended by the minims and better provisioned with food, will develop normally into typically sized workers of the various castes.

A foundress fire ant queen (Solenopsis invicta) tends her brood with the help of newly eclosed minim workers.

As the worker population increases, the queen’s careful attendance of the brood slackens and her primary role in the colony becomes egg-laying and remaining alive. Rather than standing to defend her only clutch of brood queens now have a horde of daughters to defend the nest, and they retreat from any signs of danger or disturbance to the nest.

An acrobat ant queen (Crematogaster) in formacarium with brood pile, nurses, and newly eclosed workers.

These pictures are mostly foundresses I’ve captured hunting nest sites and reared out in test tubes.  Ant colonies are fun to keep, and ridiculously easy to found (what other pet can you close away in a tube and ignore for the first month?).  For the purposes of my research I’ve mostly reared fire ant colonies, and these are the main foundresses I encounter in my area of Texas (good for my research, not so good for the ecosystems they’ve invaded).  Obviously not the ideal pet ant colony, but in a secure environment they are fun to observe and they make for sturdy, fast-growing colonies.

Home Sweet Home – Carpenter Ants

Carpenter ants (Camponotus) guard a nest entrance in a prickly pear cactus.

Carpenter ants belong to the ant genus Camponotus.  They take their common name from their nest-building habits.  Most carpenter ants prefer to nest in damp dead wood and will even hollow out dead trees.  As we’ve seen before, however, these ants can also be found in ground nests.  The above ants built a nest in the living flesh of a prickly pear cactus.  I found this group while doing field work in Argentina.  The two workers above did not approve of my nosy camera, and were standing guard over the entrance.

Although carpenter ants do not consume wood like termites do, their nest building habits can make the construction pests if they choose a building wall to tunnel in.

Ants and Hoppers

Carpenter ants tending hopper nymphs in Argentina.

Since we had the spittlebug nymphs earlier this week, I thought I’d take the opportunity to post a picture of some other hopper nymphs.  These little guys are being watched over by several carpenter ant workers, who will collect their sugary excretions and protect them from predators.

A casual observer might confuse these with mealybugs due to their white, somewhat waxy appearance and their location feeding en masse on a plant stem.  (This casual observer would in no way be me.  Nope.)  However mealybugs, like scales, have reduced appendages and secondarily lost wings.  A close look at these guys will reveal not only well developed legs peeking out, but the presence of small, developing wing buds on their backs, indicating that they are late stage nymphs (immature insects).  In fact, that dark shape near the middle left of the mass appears to be an adult thorn-mimicking treehopper, making it likely that these are members of the auchenorrhynchan family Membracidae.

At the Aphid Bar

Sugar ant (Brachymyrmex) tending aphids on flower bud.

As mentioned in a previous post, many phloem-feeding hemipterans, such as aphids, take in excess sugar, which they excrete as a substance called honeydew.  This sugary substance attracts other sugar feeding insects, which has led to some interesting interactions.  Among the most notable is the development of a mutualistic, or symbiotic, relationship between some ants and aphids.  Ants may ‘tend’ aphids, drinking the honeydew and protecting the aphids from predators in return.  This provides the additional benefit to the aphid of preventing the build up of their sugary excrement which could encourage the growth of fungi and mold.

Carpenter ants (Camponotus) tending aphids. A parasitic wasp perches on the edge of the leaf.

Ant-hemipteran interactions can be observed almost anywhere if one takes the time to observe closely.  I found the carpenter ants above tending aphids on the bushes right outside my front door.

Of course, as in any biological relationship, cheaters exist.  Some ants tend aphids without providing any protection against predators.  Some aphids manufacture less nutritious honeydew.  On the other hand, some ants take their care of aphids to extremes, even building structures to protect the aphids against winter cold.

Silhouette of carpenter ant tending aphids.

Cradle Robber

A carpenter ant worker (Camponotus) raids a Pseudmyrmex pupa from an opened nest.

While watching  Pseudomyrmex workers in an opened nest carry brood to safety (see previous post) I noticed one ant that didn’t belong.  Above you can see a carpenter ant worker who has taken advantage of the confusion to steal one of the helpless juveniles.  Although some species of ants practice brood-raiding in order to aquire ‘slave’ ants, this unfortunate Pseudmyrmex pupa will merely make a tasty meal.

Sister, sister

Dimorphic carpenter ant workers at a nest entrance.

The fine hairs on these Argentinian carpenter ants (genus Camponotus)  gave then a pretty golden sheen.  I spent a while watching the workers of this colony.  Clots of dirt extracted by diggers in the nest can be seen scattered around the periphery of the nest entrance, and form a large ring a few centimeters out.  The ants didn’t approve of my looming camera lens and I caused a bit of commotion in the ranks.

Like other eusocial insects such as termites and bees, ants divide tasks up among members of the colony.  In this case the daughter ants of the queen can take several developmental paths.  The vast majority develop into infertile workers, which carry out tasks such as nursing the young, tending the queen, building and maintaining the nest, foraging for food, and defending the colony.  As with many ants, the workers of carpenter ants are polymorphic– they may develop into different body forms, specializing in different tasks.  The large, broad headed and strong jawed ants such as the one seen above standing guard over the nest entrance are called ‘majors’.  The smaller, more typical ants such as the forager seen to the left returning to the nest, are called ‘minors.’

Many people are familiar with the concepts of ‘soldier’ and ‘worker’ ants.  The reality is more complex.  Some types of ants do not have polymorphic castes, or have a continuous range of worker sizes from small to large.  In some species of ants, the larger ants do indeed function as soldiers, while in other species they are more like pack animals, specialized for carrying large amounts of food back to the nest.  In some types of leafcutter ants, the minors ride on leaf cuttings carried by majors and defend the large ants from attacks by parasitic flies.  Smaller minors tend to be the primary nurses, as in many types of ants the major’s large jaws makes brood handling difficult.  However, in probably the majority of ants, workers progress through tasks with age, with dangerous jobs outside the nest generally relegated to the oldest workers.

The concept of the eternally busy and hard-working ant is equally inaccurate.  For example, in the typical fire ant nest, workers will often spend half their lives or more as ‘reserves’ available to be called on for a variety of tasks but otherwise inactive surplus.

Ring of dirt around a Camponotus nest entrance.

Ants and Scales

Carpenter ant workers (genus Camponotus) tend scales on a shrub in Argentina.

Scales (superfamily Coccoidea) are members of the same suborder of hemipterans as aphids, mealybugs, and whiteflies (Sternorrhyncha) but are just a little more bizarre.  They are the barnacles of the insect world.  These strange little insects have adapted to a point where they no longer need to move to gather food.  Their tube-like beaks are plugged into the plant equivalent of blood vessels, which carry nutrients to them.  Adult female scales thus no longer need trouble themselves with developing such trivial things as legs, antennae, eyes and wings, and are almost unrecognizable as insects.  The males, on the other hand, resemble small flies, and flit among plants in search of buxom, blob-like females to mate with.

While feeding on the phloem (or sap) of plants, scales take in an excess of sugar compared to other important nutrients such as protein.  To counter this, scales (and many other hemipterans) excrete a sugar rich liquid called ‘honeydew.’  Honeydew often attracts other insects such as ants, who drink the honeydew and sometimes tend the scales like milk cows, protecting them from predators.

A carpenter ant (Camponotus) tends scales on a grass blade.