Key to Theridiidae Spiders of Biosecurity Importance to New Zealand uses a set of characters that combine to narrow down the choices in order to facilitate rapid identification of specimens at the New Zealand border.

Organisation of the Lucid key to Theridiidae spiders
Lucid key operates with features (characters from the external morphology) that are considered diagnostic to particular entities (species/sexes). Each feature is illustrated with colour photos, black & white photos and/or line drawings. Each species is entered as a separate entity and represented by two additional entities - one for each sex. Fact sheets are attached to each species and contain a full set of images of both sexes (dorsal, lateral and ventral views), distribution information, a note on whether they are established in New Zealand and a reference list. Species genitalia are illustrated with black & white images.

The key has the advantage of beginning identification with whichever feature the user feels most comfortable with. By checking the boxes for each feature, the key constructs various combinations of possible entities and ranks the choices based on the reliability of the selected diagnostic features.

The key is aimed at a general audience and specialist morphological terms have been avoided where possible, so the key may not give a definite identification. Note that the main purpose of the key (as stated above) is to narrow down the choices so as to allow the user to check the genitalia of a few entities instead of going through all of them.

Diagnostic features used in this key
This key is limited to external morphological characters. They are presented below with an estimate of their relative importance to the final identification.

Identify the sex of the spider by looking at its ventral side. The distal segment of the palp in females are not expanded and adults have a sclerotised epigynum. Males lack an epigynum and their distal segment of the palp is expanded.

Body length is measured from the anterior end of the cephalothorax to the posterior end of the abdomen. Before using it, check the state of maturity because the key uses data on adults only. Variations in body length can be considerable and may not necessarily be included in the key for specimens that are out of what is considered as normal size range for the species.

The area around the spinnerets must be checked for presence/absence of colulus and its size (small vs large). This feature facilitates the identification to genus level only. Discoloured specimens and small specimens are hard to work with as the colulus can be difficult to see.

Abdomen colour is given a high importance although it is difficult to combine all variations into a few options. Colouration may seem different depending on how you look at the specimen - with or without a lens. Under magnification you may see spots that are not visible to the naked eye. Also black colouration may look more brownish under the microscope may. Colour can change due to preservation methods. Freshly killed specimens may look far different in colour to specimens that have been preserved in ethanol for many years. Consult the colour photos.

Body shape (especially abdomen) is less reliable than the colour. Check here for the correct positioning of the lateral view of the cephalothorax. The abdomen is softer than the cephalothorax and its shape may change in ethanol and can vary with the condition of the spider. It may look irregular shaped if it has shrunk. Therefore, irregular shape refers only to projections/expansions/tubercles of the abdomen.

Colouration of the legs is highly influenced by ethanol preservation. The proposed features refer to the individual segments and are mainly applicable to the first pair of legs. If these legs are missing, the features can still be used on other legs, but with less certainty. Thus, for unicoloured legs look at each segment separately, not the entire leg. When checking for bands in the middle of the legs pay attention to pigmentation (or traces of it) and not accidental dirt or ill defined spots. Use this character mainly for immature specimens, where you may need it as a character for identification.

Granulation/punctation has a minor importance and works well at the genus level. Granulation is most pronounced on the cephalothorax of Crustulina, however, some male Steatoda species have small tubercules, which can give a granulated appearance. Punctures on the abdomen are best visible under high magnification. Check for small pit-like depressions on the abdomen.

In lateral view check for presence/absence of scutum.

Use epigynum as the last step before checking the black & white images for the remaining entities. Elevated vs not-elevated is best visible in lateral view. Try to distinguish between actual epigynum and plugs left by the males after successful mating; plugs can often be gently prised out using a fine pin to reveal the genitalic structures below.

Use pedipalps as the last step before checking the black & white images for the remaining entities. All illustrations were prepared of the ventral view of left pedipalp. In a few cases an extra lateral view is provided as well.

The short cut to genera is a quick way to select species when you are certain about the genus identification. Some of the most diverse/difficult genera are represented with individual pages where species included in the key are compared on certain morphological features.

Spider diagnosis at New Zealand border
At the species level, spiders are best distinguished by their genitalia, thus only adult spiders can be reliably identified by morphological examination. Other features, such as size, colour and shape vary between the sexes of the same species, are age-dependent and can change with the preservation of the specimens in ethanol.

Although the key was designed to identify adult specimens it can also facilitate the identification of immature stages.