All webspinners have a remarkably similar body form, although they do vary in colouration and size. The majority are brown or black in colour, ranging through to a pink or reddish shades in some species, and range in size from 1.5 to 2.0 millimetres (0.059 to 0.079 in). The body form of these insects is completely specialised for the silk tunnels and chambers in which they reside, being long, narrow and highly flexible (Edgerly et al. 2002). All the females and nymphs are wingless, whereas adult males can be either winged or wingless depending on species (Ross 2009). The head has projecting mouthparts with chewing mandibles. The compound eyes are kidney-shaped, there are no ocelli, and the antennae are long, with up to 32 segments (Hoell et al. 1998).
The body is cylindrical in form, adapted for the tubular galleries within which the insects live. The first segment of the thorax is small and narrow, while the second and third are larger and broader, especially in the males, where they include the flight muscles. The wings, where present, occur as 2 pairs that are similar in size and shape: long and narrow, with relatively simple venation. These wings operate using basic hydraulics; pre-flight, chambers within the wings fill with hemolymph, making them rigid enough for use. On landing these chambers empty and wings become flexible, folding back against the body. Wings can also fold forwards over the body, and this, along with the flexibility allows easy movement through the narrow silk galleries without resulting in damage (Ross 2009).
In both males and females the legs are short and sturdy, with an enlarged tarsomere on the first pair, containing the silk-producing glands (Collin et al. 2008). The abdomen has ten segments, with a pair of cerci on the final segment. These cerci are highly sensitive to touch, and allow the animal to navigate while moving backwards through the gallery tunnels, which are too narrow to allow the insect to turn round (Hoell et al. 1998). Because morphology is so similar between species, it makes species identification extremely difficult. For this reason, the main form of taxonomic identification used in the past has been close observation of distinctive copulatory structures of males, (although this method is now thought by some entomologists and taxonomists as giving insufficient classification detail) (Szumik 2008). Although males never eat during their life span, they do have mouthparts similar to the females. These mouthparts are used to hold onto the female during copulation (Arnett 2000).
- Arnett, Ross H., Jr. 2000. American InsectsA Handbook of the Insects of America North of Mexico: A Handbook of the Insects of America North of Mexico, Second Edition. CRC Press.
- Collin, Matthew A., Jessica E. Garb, Janice S. Edgerly & Cheryl Y. Hayashi (2008). "Characterization of silk spun by the embiopteran, Antipaluria urichi". Insect Biochemistry and Molecular Biology 39 (2): 75–82.
- Edgerly, J. S. , J. A. Davilla & N. Schoenfeld (2002). "Silk spinning behaviour and domicile construction in webspinners". Journal of Insect Behavior 15 (2): 219–242. doi:10.1023/A:1015437001089
- Hoell, H. V. , J. T. Doyen & A. H. Purcell (1998). Introduction to Insect Biology and Diversity (2nd ed.). Oxford University Press. pp. 389–391. ISBN 0-19-510033-6.
- Ross, E. S. 2009. Embiidina. Pages 315-316 in Encyclopedia of Insects, V. H. Resh and R. T. Cardé, eds. Academic Press, New York.
- Szumik, Claudia (2008). "Phylogeny of embiopterans (Insecta)". Cladistics 24: 993–1005. doi:10.1111/j.1096-0031.2008.00228.x