Preparing Ants for Study

For short term storage, ants can be placed in 75% to 95% ethanol (also called ethyl alcohol). They should be kept cool and in darkness and should not be allowed to dry out. After initial collecting, the alcohol should be changed to assure that the concentration is appropriate (it can be diluted by body fluids when first collected). Also, any dirt, plant material or other debris that was collected with the ants should be removed. This material can stain the ants if left with them for extended periods. It is especially important that the tubes be stored in the dark as light will cause colours to fade and the cuticle or integument will deteriorate over time, greatly reducing the usefulness of the material for taxonomic studies and making identifications difficult or impossible.

Pinning
For detailed study and long-term storage, ants should be point-mounted on insect pins. Pointing allows specimens to be easily manipulated while being examined with a microscope and is essential for viewing fine details such as sculpturing and pilosity. In all cases, ants, even large species such as those in the genus Myrmecia, should be placed on points and not directly pinned. This is because the mesosoma is relatively thin and in many species there is a flexible suture between the pronotum and mesonotum. If a pin is placed through the mesosoma the pronotum will often break away from the mesonotum, seriously damaging the specimen.

A commonly used procedure for curating ants is as follows. Field-collected specimens are transferred from the original collecting vial to a small dish and covered with alcohol. Several specimens are selected for mounting, with the exact number depending on several factors. For example, if the species is represented by only a single caste (no major or minor workers, or queens or males present) then about 6 workers should be sufficient. If, however, the species is polymorphic or queens or males are present, then representatives of all castes should be selected.

Another factor influencing the number of specimens is their size. It is desirable to place 2 or 3 workers on separate points but on the same pin. This saves space in collections, allows several specimens to be examined at the same time under the microscope, and associates polymorphic workers with each other and queens and males with workers. Because of this it is common to mount ants in sets of 3. For example, 3 workers on each of 2 pins, or a queen, male and worker on a single pin, or a major, medium and minor worker on a single pin. Large species should mounted similarly, but in sets of 2 on 3 pins. The remainder of the series can be stored in alcohol for future use.

Individual points can be either hand-cut from strips of stiff, white, high-quality, acid-free paper, or punched with a specially designed hand-punch. The use of a punch is preferable if large numbers of ants are to be mounted as it produces points quickly and of uniform size and shape. The glue used to attach ants to the points should be water-soluble to allow for later removal if needed. Stainless steel insect pins of size 2 or 3 can be used to hold the points.

Individual ants should be glued to the tip of the point with just enough glue to hold them securely but not so much that the lateral or upper surfaces are obscured. It is best to place the point so that it contacts the basal segment (coxa) of the mid- and hind legs. Specimens should be mounted upright, horizontal and with the point extending from the ant’s right side. Another important procedure is to very gently position the legs so that they do not obscure the body when viewed from the side. This is one of the more difficult aspects of mounting ants but is also one of the most important as identifications will be difficult if the specimen can not be viewed clearly. Finally, the number and configuration of mandibular teeth are important characters in many groups. If possible, at least 1 of the mounted specimens should have the mandibles open so their inner margin is visible. A careful inspection of the available specimens will often reveal individuals which are in better positions for mounting. These individuals should be selected as they will help in reaching a better final result.

There are two common methods of placing ants on points. The first is to place the point on the pin and then glue the ant to the upper surface of the point. The other method is to lay the ant on its back and then glue the point (without a pin) to the underside of the ant. Once the glue has dried, the point plus ant can then be turned upright and placed on a pin. The first method works satisfactorily for small ants but generally not for larger specimens. When placed on top of a point, larger specimens tend to tilt or even fall off before the glue can dry. Because of this, the second method is preferable, especially for large specimens, and is often used for small ants as well. With this method, the tip of the point can rest on the ant while its base rests on the table or microscope until the glue dries. This minimises tilting of the specimen and results in a higher quality preparation.

What to do
In summary, the most important things to remember when pointing ants are: Always use points and never directly pin ants. Use only enough water-soluble glue to hold the ant on the point without using so much that it covers the sides or upper parts of the specimen. Place the ant at the very tip of the point with the point covering the first segment of the middle and hind legs nearest the body. Keep the ant upright so that it is positioned on top of the point with the long axis of the body horizontal and at right-angles with the point, the upper surface of the body upwards and the length of the point towards the right side of the ant. Try to (very) gently pull the legs downward so that the outer surface of the body can be seen in side view and open the mandibles so that their inner margins are visible.

What NOT to do
A few things to avoid include: Direct pinning through the body. Burying the ant in glue. Placing several ants on a single, large card. Placing the specimen on its side, or upside down. Having the legs up over the sides of the body.

Labels
Once the specimens are properly mounted, the final step is to add labels. Labels are the standard type used in entomology, and include as a minimum the location (state and nearest named place), date and collector’s name. Additional information which should be included if available include the latitude, longitude and elevation of the collection site, a brief description of the habitat, and the collection number (if used). The use of collection numbers alone should be avoided as this information is useless if the collection notes are not available. This last point is especially important if material is to be deposited in another collection or museum, or is to be sent to a specialist for identification. The value of the specimens will be greatly increased if biological information is included on the labels. Often, especially in the future, these short notes may be the only information available regarding these specimens and will provide the only clues as to their biology.

How others do it
Jack Longino