How to collect ants?

Ant collection method 4 Winkler extraction
Ant closeup 1

How to collect ants?

Aside from the ecological habits of ants to live in specific microhabitats (e.g., on trees, within leaf litter, above the ground, within soil), ants’ activity may also differ between different time of day, with some species being diurnal while others are nocturnal; or even only active at particular time of the year (e.g., wet season vs dry season). This means that even by staying at the same location, but by using different sampling methods and at different time we will collect different species! So how to start collecting ants?

Getting started

First, we need to decide what sampling methods we want to use. Some methods are relatively simple and straightforward, so they can give us a quick overview of what kinds of ants are present in the habitat, but we may very likely miss many of the rarer or more cryptic species of ants. Other methods require specific equipment or devices that are designed for the purpose. These methods specifically target a particular niche in the habitat (e.g., subterranean, leaf litter, arboreal), they give us a more in-depth knowledge of what species are present in that niche, but they also require more efforts, usually are more time-consuming and require the acquisition of specific equipment.

Method pooter
An entomological aspirator. Air suction is created through the long plastic tube using our mouth. There is an air filter in the cap of the vial to protect the user from breathing in soil particles.

The simplest and most straightforward method for collecting ants is what is known as ‘hand collecting’. Of course, we are not really collecting using our hands. We use a simple device called entomological aspirator (or ‘pooter’ by entomologists) to suck ants that we spot into a vial indirectly through a tube (creating an air suction with our mouth). We first identify potential good places where ants may live (on trees, on lower vegetation, under a stone, inside decaying wood on the ground, etc.) and start looking for ants. We can also incorporate other methods such as soil sifting and vegetation beating to help reveal ants that may be hard to spot directly.

A colony of Camponotus sp. cf. mitis was found inside a decaying wood on the forest floor in Saiyuen. Ants revealed by shaking and breaking up the wood were captured using an aspirator.

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Baiting is also a frequently used methods to attract ants, and allows us to collect them near the bait. Because ant species have different food preference, it is possible to use different food type such as sugar or protein, or a combination of them to attract more species.

Method baiting closeup
Processed meat used as protein bait, which attracted Crematogaster sp.

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Advanced methods

As we are only able to collect ants that we see, hand collection has many limitations. For example, if we sample during the day, we are unlikely to be able to collect ants that are active during the night. It is also not very good at collecting ants that are relatively small (<3 mm) or active within leaf litter or underground. So how do we collect these ants? We can use something called pitfall traps. It is also very simple: we bury a small cup partially filled with alcohol (ethanol) in the soil, with its rim in level with the ground, we then return and collect it one to several days later. Comparing to hand collection, pitfall traps are static and can only collect ants that are active above the ground. But since it is set up for a much longer period of time, it can tell use a lot more about what ants are present in the habitat regardless of when they are active during a day.

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A similar approach but this time targeting ants that are active beneath the ground is called subterranean traps. The trap is buried beneath the ground and come with baits to better attract ants (subterranean ants rely heavily on olfactory sense!). The trap is covered with a lid this time and, instead, small holes are pierced on the side of the cup to give access to the ants. Other common methods we use include Winkler extraction and Malaise traps. The former target ants that are active within leaf litter, while the latter is able to capture winged reproductive castes of ants: queens and males. These two methods, however, require the purchase of specific equipment which is not so easy to find.

Method winkler sifting
Method winkler bag
Method winkler bag closeup
Winkler extraction involves sifting leaf litter (first), which is then bought back to laboratory and suspended inside a Winkler bag for days (second and third). A small cup partially filled with ethanol is placed at the bottom of the bag to collect ants (and other soil arthropods) that fell from the litter over time.

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Ant specimens collected are stored in alcohol for better preservation. We also record when, where and how they are collected in details, which can tell us their distribution and what habitats they preferred. For the identification of species, we use previously published literature and specimen photos as reference. If they cannot be identified without first being placed under the microscope for careful inspection, or they are rare collected, or we want to take specimen photos for future reference or publication, we will dry and mount them by gluing them on a paper card point. We want to make sure mounted specimens are kept in good condition for decades, so they will be stored with other ant collections inside a room with controlled temperature and humidity.

Collection 1
Collection 2
Mounted ant specimens are sorted by taxonomy and stored inside specimen boxes (first). Each specimen is labelled with collection data, a unique specimen code and its identified species (second).

And this is how we collect, identify and organize ant specimens! By first knowing what ant species we have and how they are distributed, we can then understand the ecology and diversity of ants in Hong Kong.

If you want to learn more about ants in general and, perhaps, the identification of ants, below are a few websites that are freely accessible and offer some useful tools and guides:

  • AntWeb: an incredible resource presenting high magnification pictures for thousands of ant species.
  • AntWiki: another incredible resource functioning like a Wikipedia dedicated to ants with information about their biology, morphology and with many taxonomic keys on how to identify ants.
  • antmaps.org: if you want to know where different genera or species of ants are found around the world, this is the place to go with all 15,700 species mapped!
  • YouTube Channel of the Insect Biodiversity and Biogeography Laboratory from the University of Hong Kong, with all the above embedded short videos demonstrating different collection methods (and more!).

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Ant Overview

Glossary

A･B･C･D･E･F･G･H･I･J･K･L･M･N･O･P･Q･R･S･T･U･V･W･X･Y･Z

A

Alate queens / alate males. Queens or males that are born with wings and are capable of flying. After mating, queens would shed their wings and are now known as dealate queens.

Antennal club. Apical segments of the antenna that are distinctly enlarged.

Antennal scape. The basal-most segment of the antenna that is elongated.

Arboreal. Nesting and/or active on trees.

Army ants. Ants that do not build permanent nest and are constantly on the move. They often forage collectively in mass.

B

Brood. Non-adults, including eggs, larvae and pupae.

Budding. New queens leaving with some workers and brood from the original colony and found a new colony nearby. In contrast with alate (winged) queens founding a new colony alone after mating.

C

Castes. Roles of ants in the colony, usually predetermined before they become adults. Defined by sex, morphology and reproduction capability of the ants. Further subdivisions based on minor differences in morphology and role are known as subcastes.

Clypeus / clypeal margin. The anterior part of the head, in-between the insertion site of antennae and the mandibles of the ant. Clypeal margin refers to the anterior margin of the clypeus.

Coccids. A family of insects (Coccidae) belonging to the infraorder Coccomorpha (scale insects) of order Hemiptera, also known as soft scales or wax scales. They may form mutualistic relationship with ants, offering honeydew in return for protection.

Colony. The social structure of ant, constituted by workers and reproductive individuals that cooperate with one another, as well as their brood. Members of the same colony are able to recognize and are not aggressive with each other. Number of individuals can range from a few to several millions.

Cosmopolitan distribution. Global or near global distribution.

Cryptic. Obscure lifestyle, often refers to subterranean species and species that are active within leaf litter.

D

Dimorphic. There are two distinct subcastes for workers. There is no intermediate form in-between the two subcastes.

Disturbance / disturbed environment. Human activities that change the environment and impact ecosystem, which can be momentary or prolong. Agriculture and environmental management (e.g., cutting or trimming trees, use of pesticides) are two typical examples of the disturbance that may affect ants.

Dorsal view. Top-down view on an ant.

E

Epigaeic. Nesting and/or active above the ground and on lower vegetations.

Ergatoids. Queens or males that are born wingless. Ergatoid queens may look very similar to workers.

Exotic species. Species that has been introduced to place outside of where it is originated from (=introduced species).

F

Forage. Hunting or gathering food.

Full-face view. Frontal view on the head of an ant.

G

Gamergate. Workers that have mated with males and are able to lay fertilized eggs for reproduction. Depending on the ant species, gamergates may coexist with queens, or entirely replace queens.

Gaster. The posterior part of an ant’s body, connected with mesosoma through waist segment(s). In some ant species a sting is present at the end of the gaster for hunting and/or self-defense.

Gastral tergites. The dorsal part of the gaster, can be subdivided into segments.

H

Habitat. Where the organism live, characterize by the landscape and dominant plants (e.g., tree, shrub, grass, mangrove tree) present.

Hemiptera. An order of insects that includes aphids, cicadas, leafhoppers, scale insects and shield bugs. Most of them feed on plant sap, and sometimes form mutualistic relationship with ants, offering honeydew in return for protection.

Hypogaeic. Nesting and/or active within or below leaf litter, inside rotten woods, beneath rocks and within the soil.

I

Intraspecific variation. Variation between individuals of the same species, in contrast with interspecific variation, which describe variation between species.

Introduced species. Species that has been introduced to place outside of where it is originated from (=exotic species).

Invasive species. Species that has been introduced to place outside of where it is originated from and has a significant impact on the local ecosystem.

L

Leaf litter. The layer of plant debris above the soil, which is made up of fallen leaves, branches, fruits, seeds and flowers.

M

Mandibles. The pair of hard mouthparts of insects for biting, cutting and holding food. It is a part of the exoskeleton.

Mesosoma. The anterior part of an ant’s body, connected with gaster through waist segment(s). It is also where the legs and wings (when present) of the ant attached.

Microhabitat. Where the organism live, at a finer scale than habitat. It is further characterized by the local temperature, humidity of the environment. For example, beneath a rock and on the surface of tree branches are two different microhabitats of the same habitat (forest).

Monogyny. Colony with only one egg-laying reproductive individual.

Monomorphic. There is only one size and form for workers, and cannot be further subdivided into subcastes.

Morphology. The form and structure of an organism, both internal and external. For external morphology, it includes the shape, size, color, pattern and external structure of the various parts of the organism.

Morphospecies. A species defined solely base on its morphological differences with respect to other species. It may not have been formally described and named.

Mutualism. Mutually-beneficial relationship between organisms.

Myrmecophily plants. Plants that are positively associated with ants.

Myrmecophyte plants. Plants that have formed mutualistic relationship with ants, and possess adaptations for such relationship, such as food bodies and extrafloral nectaries dedicated to ants and/or specialized structure for ants to nest (e.g., hollowed structures in tree branches).

N

Native species. Species that that naturally live in a particular place without human intervention. ‘Native fauna’ further specifies animal species, while ‘native flora’ specifies plant species.

Nest. The physical structure that ant colony lives in. It may be permanent and extensively built, or temporary and has only been minimally modified by its residents.

Niche. It can broadly refer to the role an organism plays within its habitat, or specifically refer to where an organism lives within its habitat. Here niche means the latter.

O

Oligogyny. A special case of polygyny, where there is more than one egg-laying reproductive individual in an ant colony, but these individuals do not tolerate one another and stay far apart from each other in the nest. Workers still cooperate with one another like in a normal polygynous colony.

Open habitats. Habitats such as open shrubland and grassland, in oppose to habitats with dense vegetation cover, such as forest.

P

Parthenogenesis. Asexual reproduction through unfertilized eggs. For ants, it means reproductive females are able to reproduce partial or complete clones of themselves without mating (i.e., theylotoky).

Pest. Species that has been a source of nuisance to people. Common categories include household pest and agricultural pest (which causes damage to crops).

Petiole. The first segment of waist segments (or the only segment, when there is only one waist segment) of an ant, connecting mesosoma and gaster. It may be reduced and difficult to observe.

Polygyny. Colony with, on average, more than one egg-laying reproductive individual. Facultative polygyny (=secondary polygyny) means that colonies were originally monogynous when founded, but would later adopt other queens (usually daughter queens of the colony) and become polygynous.

Polymorphic. There is more than one size and/or form for workers, hence, can be further subdivided into subcastes. When there are two distinct subcastes but no intermediate form, it is known as dimorphic.

Postpetiole. The second segment of waist segments, connecting mesosoma and gaster. Some species of ants do not have a postpetiole.

Profile view. Side view of the ant, usually with its head facing left.

S

Scale Insects. An infraorder of insects (Coccomorpha) belonging to the order Hemiptera, also includes coccids. They may form mutualistic relationship with ants, offering honeydew in return for protection.

Scavenger. Ants that predominantly gather food instead of through other means, e.g., hunting. Depends on the ants’ preference, it may include fruit, seed and other food bodies of plants, carcasses of invertebrates and small vertebrates, honeydew produced by other insects, etc.

Sculpture. Pit- or grove-like structure on the surface of the exoskeleton of the ant, in contrast with smooth and shining surface. Its pattern can be used to differentiate between species of ants.

Secondary forest. A forest that has been regrown after timber harvest or agricultural activities, in contrast with primary forest, which has not been deforested by human. There are only secondary forests in Hong Kong.

Soil arthropods. Small invertebrates from the phylum Arthropoda that are active within and above the soil, as well as within leaf litter.

Spine. Hard and pointed structure on the back of the ant. It may be long and sharp like a thorn, or low and inconspicuous. It most often appears at the posterior part of mesosoma in one pair (propodeal spine), with other possible locations include pronotal spine and petiole spine.

Subcastes. Roles of ants in the colony, a further subdivision based on minor differences in morphology and role under their respective castes.

Supercolony. The unusual case where multiple colonies unite and are not aggressive with one another, often occur in invasive species in introduced regions. Individuals range from millions up to billions.

T

Tramp species. Species that are associated with habitats frequently-disturbed by human activities. They may further be dispersed by human to places beyond its native range.

Trophic eggs. Unfertilized eggs that function as food. In ants, they are usually produced by workers and offered to queens and larvae.

W

Waist segment(s). The segment(s) connecting mesosoma and gaster of an ant. The first segment is called ‘petiole’ and the second segment (when present) is called ‘postpetiole’.

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