They are eyeless and blind, and bear spiracles on all leg-bearing segments—in contrast to other groups, which usually bear them only on their 3rd, 5th, 8th, 10th, 12th, and 14th segments—a "mid-body break", accompanied by a change in tagmatic shape, occurring roughly at the interchange from odd to even segments.
Son cegos e levan espiráculos en todos os segmentos que portan patas, a diferenza doutros grupos que xeralmente os teñen só nos segmentos 3º, 5º, 8º, 10º, 12º e 14º, cunha "rotura a metade do corpo", acompañada por un cambio na forma dos tagmas, que se produce no paso dun segmento impar a un par.