DESIGN OF INSECT UNGUITRACTOR APPARATUS

The structure of the unguitractor system of insect legs was studied us ing scanning and transmission electron microscopy. On the base of seri al semithin sections, the 3-D reconstruction of structures of the term inal tarsomere was obtained and the arrangement of different types of cuticle was demonstrated. The membrane connects all structures of the system and divides the terminal parts of the claw flexor muscle into t he external (unguitractor plate) (UT) and inner (tendon) ones. Elastic nonlayered cuticle located between the claws and the posterior wall o f the terminal tarsomere is interpreted as a claw-returning string. Cu ticle surrounding the apodeme of the posterior wall of the terminal ta rsomere contains large porous canals. The anterior part of the termina l tarsomere has an invagination that forms a plate facing toward the U T. This plate comprises the UT anteriorly and laterally and contains a microtrichia field (MF) on its distal part. The surface of the UT has a complex microstructure providing fixation to the MF of the correspo nding surface of the anterior wall of the terminal tarsomere. Microtri chia of the UT and MF are directed to opposite directions and provide anchorage of the UT whenever the flexor claw muscle contracts. The mic rosculpture of UT and MF for representatives of Odonata, Coleoptera, H emiptera, Hymenoptera, and Diptera was compared. It is suggested that small insects, which are able to walk quickly on thin rods, usually ha ve wide microplates on the UT plate to provide quicker fixation-releas e of the UT in the contact area, Insects using the legs to produce hol lows in the soil usually have a large UT with well-developed microtric hia on its surface to produce strong friction forces in the contact ar ea for a long period of time. (C) 1996 Wiley-Liss, Inc.