Hadrurus arizonensis, Ewing, 1928

Farley, Roger D., 2011, Pectine development in scorpion embryos and first and second instars, Euscorpius 120 (120), pp. 1-47 : 5

Hadrurus arizonensis ( Caraboctonidae )

As in earlier examples (Figs. 2 − 4, 7), an elongate pectine can be seen at the ventro-lateral wall of the mesosoma in the embryo of Figure 12. Some transverse striations are also present. The chelicerae are anterior to the mouth, and the pedipalps are segmented and divided distally. The metasoma has all five segments, a tapered telson and is sharply flexed ventrally. This embryo is unusual in having very large tergites on the segments of the mesosoma. These may facilitate gas exchange as hypothesized for the dorso-lateral processes in embryos with katoikogenic development (Figs. 18, 20, 28 − 30; Mathew, 1956; Farley, 1999). The legs are slender and tapered distally (digitigrade) in contrast to the plantigrade legs of second and later instars ( Jeram, 2001; Farley, 2005). The plantigrade form is thought to be an adaptation for terrestrial locomotion ( Jeram, 2001).

The pectine in Figure 13 is at about the same stage as the embryo in Figure 12, but is shown here at higher magnification. The slender, ribbon-like pectine has transverse striations, and an elongate groove (asterisk) has started to separate the pectine into anterior and posterior regions. The anterior part of the pectine is an integral part of the body wall while the posterior edge of the pectine appears to be slightly separated. The striations anterior to the groove are decreasing while those posterior to the groove are prominent and will continue as separations of the pectinal teeth. Embryo pectines with a longitudinal groove are shown in Figures 4, 21 and 22. In Farley (1999, Fig. 69; 2001c, Fig. 6), the pectinal groove is evident but not labeled or correctly described for embryos of Smeringurus mesaensis