Comparative study of the morphology of stridulatory organs of the Iberian lycaenid butterfly pupae (Lepidoptera)

We compared the pupal stridulatory organs of 35 species and one subspecies of Iberian Lycaenidae using scanning electron microscopy. The studied species belong to the tribes Theclini, Eumaeini, Lycaenini, and Polyommatini. Nine species do not show stridulatory organs on the pupae but all other species possess them. Stridulatory organs are formed by a stridulatory plate (pars stridens) placed on the fifth abdominal segment and a file (plectron) in the sixth abdominal segment. The plate has tubercles in the Theclini and Lycaenini, tubercles, ridges, or undulations in the Eumaenini, and tubercles, teeth, or unspecialized structures in the Polyommatini. Morphological differences can be found in the files of the different tribes, regarding the number of teeth, their form and size. Cuticular formations of the organs were studied on a surface of 2,500 µm(2) and the average of ridges, tubercles, and teeth was measured searching for relevant taxonomic information. Stridulatory organs were thought to be an adaptation to myrmecophily but we show that they are present both in myrmecophilous and nonmyrmecophilous species; therefore, we suggest that this trait probably did not evolve in relation with myrmecophily, but may be used to enhance relationships with ants.