Sweep netting, vacuum sampling, sticky traps, Malaise and light traps may all be used to sample leafhoppers, planthoppers and psyllids. But all these methods have the disadvantage that you may learn little about the host plant. It is possible to sweep or vacuum from individual plant species.
Sweeping has the advantage of being simple. Many short-winged forms will be captured in sweep samples, although species that live low on plants or in the thatch may be missed. Vacuum sampling may be more effective at producing the more uncommon species. It is generally easiest to process net contents in the field by holding the net open and aspirating planthoppers as they attempt to escape.
Malaise traps are a type of interception trap and an excellent way of passively collecting many types of insects. They may be left unattended for some days, the catch accumulating in pots of alcohol. Some species may often appear in large numbers in Malaise samples, although brachypterous forms are, not surprisingly, not often collected.
Sticky sheets, especially yellow in colour, are often used to monitor insect pests in greenhouses. However, they can also be used to monitor and sample flying insects in the field. Double sided yellow plastic sheets can be covered in sticky glue- or can be purchased ready prepared. Sheets may be hung among crops and also may be hoisted into the canopy of trees, where it may give some indication of those insects flying around the canopy. The glue which is frequently used may be dissolved in ‘white spirit’ to remove specimens.
Many leafhoppers and planthoppers are attracted to light, sometimes in large numbers. It is difficult to be sure where species have been feeding but it is a good way to obtain specimens of many species.
Vacuum sampling may be one of the most effective ways of sampling delphacids and many leafhoppers, especially those that live low on the plant or in thatch that would otherwise be missed by sweeping, and would not ordinarily come to Malaise or light traps. Many now use inexpensive vacuum samplers, which are modified garden ‘leafblowers’ or ‘blower vacs’. The modification is to add a mesh net to the inlet tube (by tape, rubber bands or metal clip) of a petrol powered (2-stroke oil-petrol mixture) leaf blower that has been arranged for vacuuming. This type of arrangement is excellent for sampling short grass habitats or grass or sedges that grow in clumps that otherwise could not be sampled by sweeping. Samples taken this way can be processed in the field similar to a sweep sample.
Specimen preparation for identification
Identification of specimens to species level usually requires males, and often the male genitalia need to be 'cleared' for examination. Clearing the male genitalia involves breaking off the abdomen and placing it in 10% potassium hydroxide (KOH; or sodium hydroxide, NaOH) solution. A cold KOH solution may be used, with the specimens left overnight for clearing or hot KOH can be used to clear specimens within a short time. KOH (particularly hot KOH) is caustic and care needs to be taken in both its use and that specimens may become ‘over-cleared’. To prepare the genitalia the abdomen needs to be removed from a specimen. This may be achieved by turn the specimen upside down and push gently on the abdomen (to avoid damaging the genitalia, do not press on the pygofer); usually the abdomen will snap off at the base (at the tymbal mechanism. Sometimes the abdomen may suddenly snap off – it is a good idea to clean you workspace and perform this task within some type of container so that the abdomen can be easily found if abruptly dislodged. The abdomen can then be placed in KOH for clearing. Specimens and their separated abdomens need to be clearly associated to avoid any confusion later, especially if making multiple preparations. This is usually achieved by numbering the specimens and the clearing tubes.
A cleared abdomen will still have colour, but will be flexible without being brittle. The soft parts of the anatomy will be easily dislodged and removed. When the abdomen is ready to be removed from the KOH, rinse the abdomen in water and gently remove the contents to remove any remaining KOH (multiple rinses may be desired, or carefully neutralizing the KOH with a mild acid), then move the abdomen into glycerin. Sometimes the cleared abdomen will be sufficient to view the needed features, but often the aedeagus will need to be everted.
Labelling specimens and Vouchers
It is essential that specimens preserved for later study or storage are labelled fully and clearly. While the insect specimen itself may provide information regarding color or morphological variation of the species, it is the insect label that provides most of the information about the temporal and special distribution of a species, habitat and host records. The label information should also be precise, unequivocal, and self-explanatory so that users of the specimens will be able to properly interpret the label data, and abbreviations should be used with care so that they are understandable in the context of the label information. The details of how the information is organized on the labels are less important than having the label information clear and complete. Suggested information and format for the label information is organized from general to specific (often with the country in all caps), GPS data for the locality is also increasingly important; date collected (day, month, year, with month in roman numerals), collector, collecting method, habitat or host plant (when known).