The Urban Pantheist

The presence of the jeweler's loupe here is a hint that this is a very small organism. We generally think of ants as small animals, but this species is the smallest I've ever seen. Each worker is just about 1 mm in length.


Their size and distinctive coloration--dark in the front with light legs and abdomen--identifies them as ghost ants Tapinoma melanocephalum*. Like many inhabitants of the great indoors, their origin is not precisely known. They are from the Old World Tropics for sure, narrowing it down to roughly a third of the surface of the planet.


A colony could form in a pile of dead leaves, or in between a plant pot and it's protective liner. As long as the place is warm and humid, the ghost ants can live happily, feeding on miniscule amounts of sweet things and dead insects. When a colony is successful, some amount of it departs to become a new colony--"budding" instead of the complex new colony creation that some other eusocial insects endure. Besides all the tropics and heated greenhouses in the world, ghost ants live in Florida and Texas, and appear to be spreading.

* Humble and dark-headed

When people tell me they have ants indoors, I ask how big. If they say small, they're probably pavement ants or odorous house ants that are nesting in the cement of the floor or foundation. If they say big, well, then I know the building is in need of repair. Often I'll ask if the ceiling leaked last time it rained--usually it did. These eastern black carpenter ants Camponotus pennsylvanicus* only move in if there's some nice water-damaged wood for them to nest in.

The main nest is in the dead part of a live tree. The ants travel across the branches at night, into the upper levels of wood construction of a building. If there's water damaged wood they can work with their mandibles, they'll bring over several dozen of their larvae. They bring the larvae not just to have a ready-made supply of new workers, but to help them eat. Adult ants can't eat solid food, so they bring bits of insects to the larvae, who chew them up and regurgitate liquid the adults can lap up. Besides dead insects, carpenter ants like sugar-rich foods, like aphid honeydew and discarded and carelessly stored human food.

Carpenter ants are a critical part of the forest ecosystem. They move into trees that have been weakened by fungi to build their nests. Large woodpeckers come to feed on the colony, opening up cavities in the dead wood. Cavity nesting birds depend on these sites to reproduce. Wood ducks, for example, are unable to make their own cavities in which to nest, and thus depend on woodpeckers, carpenter ants, and wood decaying fungi in order to successfully reproduce.

* Camponotus means "flat back", referring to the flattened or weakly curved dorsal mesosomal profile of most Northern Hemisphere species.

A coworker called me over to identify some insects lurking in a mealworm colony. They were so small (about 2 mm long each) I couldn't even tell what they were at first--I actually thought they were fruit fly pupae.

I took this picture and could see that they were beetles. Not sawtooth grain beetles, because these lack the distinctive teeth on the thorax. I went to my pest control text, since it seemed likely that they were known grain pests.

It soon became clear that these were flour beetles (Tribolium sp.). There are two common types, T. castaneum the red flour beetle--so called because of the reddish brown color--and T. confusum the "confused" flour beetle, which gets its name because it's easily confused with the other. Really. The "confused" is more tolerant of cold temperatures, and is more common in northern climates. However, the red has another field marking that helps remove the confusion: it flies, while the other does not. I was told these beetles had been observed flying, allowing me to identify them to species.

I was also interested to learn that both kinds of flour beetles are in the family Tenebrionidae: the darkling beetles. Darkling beetles are what I call the adult form of mealworms. So the mealworm colony was infested with their own tiny cousins. Hard to consider them contaminants, more like freeloaders.

A fourlined fringetail (Species #16 Ctenolepisma lineata) briefly pauses its mad dash across the bathroom tile.

The insect order Thysanura* (which means "fringe-tail," referring to the two long cerci** and middle abdominal segment making a three part "tail" of sorts) includes the famous silverfish and somewhat less well-known firebrat. The family also includes this species, which is apparently native to southern Europe, but found along the east coast of North America as well as in California. It may go without saying that it is almost always found indoors, and humans are the cause for it being found so very far from its original range.

Creatures in this order are spectacularly omnivorous, feeding on substances such as bookbinding glue and wallpaper paste. The fourlined fringetail is among a very small number of animals that can digest cellulose (cows and termites cheat by having guts packed with cellulose-digesting microorganisms).

This is the first appearance of this species on this blog! The related species that is actually silver (owing to covering of slippery scales) was 365 Urban Species #275.

* It appears that more up-to-date writers use the name Zygentoma for the order.

** Cerci are also the "pincers" at the back of an earwig, and the sensory tails at the back of a cockroach.

I leaped to this brash identification with the help of these websites:
The indispensable bugguide.net.
UC Riverside's website on Urban Entomology.
I made up the common name.

Fruit fly Drosophila melanogaster

Dark-eyed fruit fly Drosophila repleta


There are several species of very small flies that one is likely to find in a kitchen. Besides the little house fly and the drain fly, there are a few types of fruit fly, including these two. Identifying small flies is important if you are interested in reducing their numbers, since different substances attract different flies.

D. melanogaster is attracted to the products of fermentation. A ripe fruit is just the thing to make these tiny reddish flies magically appear; a banana peel in the trash will work too. The fruit flies are there to lay eggs in the rotting fruit—their larvae will feed on the sugars and yeasts found there. Vinegar and wine come ready-made with these ingredients and open containers of these will also attract fruit flies.

D. repleta is a slightly larger fly, darker all around, with eyes that are noticeably darker than D. melanogaster’s. The dark-eyed fruit fly is not as interested in fruit—it is attracted to the bacterial scum that forms in places where food and water collect. A crack in a kitchen floor is an ideal nursery for dark-eyed fruit fly maggots, as are many parts of a dirty sink. D. melanogaster infestations last as long as the fruit is around, D. repleta infestations are long term, requiring deep cleaning of surfaces and cavities that are never otherwise cleaned. Products containing microbes that consume the bacterial slime that harbor dark-eyed fruit fly maggots are a safe and reportedly effective way to eliminate them. D. repleta is part of a complex of closely related species which fly geneticists are still trying to untangle and understand.

D. melanogaster is among the most important of all urban animals. Their rapid and profuse reproduction (under ideal conditions they can go from egg to adult in about a week) and the ease with which they can be raised in captivity, have made them ideal lab animals for genetic studies. Much of what science knows the building blocks of life and how they work is directly due to the study of these humble vinegar flies. Only the house mouse can compare when it comes to animal species that have contributed to the body of knowledge we have about ourselves.