Soldier head morphology of the Neotropical termites: Embiratermes festivellus Silvestri and Spinitermes brevicornutus (Desneux) (Isoptera, Termitidae)

Abstract

ABSTRACT. Heads of soldier termites belonging to the species Elllbiralermesjeslivel/us (Silvestri, 1901) (Tennitidae, Nasutitermitinae) and Spinilermes brevicorl1l1ll1S (Desneux, 1904) (Termitidae, Termitinae) were examined using scanning electron microscopy. Individual glandular openings are present in the upper part of E.jeslivel/lls head and correspond to class 3 glandular cells. Campaniform sensillae occur in both termite heads, but this sensorial structure was not observed in the nasus extremity of E. jeslivel/lls soldier.

The evolution of symmetrical snapping in termite soldiers need not lead to reduced chemical defence

“…The gland reservoir is restricted to the frontal projection and does not protrude down to the head cavity, entirely occupied by hypertrophied mandibular muscles. Such a position of the gland has been observed previously in the related genus Spinitermes , having slashing/piercing mandibles as well as in the other higher termites with well‐developed mandibular defence, for example the nasutoid soldiers from the subfamily Syntermitinae (Costa‐Leonardo & Barsotti, ; Santos & Costa‐Leonardo, ). By contrast, the soldiers of Nasutitermitinae have reduced mandibles and their gland reservoirs thus can extend up to the posterior part of the head capsule behind the brain, devoid of mandibular muscles (Quennedey, ; Santos & Costa‐Leonardo, ).…”

“…While blocking the nest passages with their heads, the soldiers may apply the snapping mechanism, considered to be shaped for the use in confined spaces (Prestwich, ; Scholtz et al ., ), as well as the frontal gland products, draining from the frontal pore situated inside the frontal cavity (Fig. C, D), just as in Spinitermes and some other Termitinae (Costa‐Leonardo & Barsotti, ; Rocha, ) and unlike in Nasutitermitinae and Syntermitinae having the frontal pore at the point of the frontal tube.…”

“…However, the presumed absence of the chemical defence in symmetrical snappers is not as obvious. The soldiers of these genera have characteristic frontal projections in the anterior part of their heads that may signal the presence of a functional frontal gland, just as is the case of the related non‐snapping genus Spinitermes (Costa‐Leonardo & Barsotti, ). In addition, the frontal pore, although small and inconspicuous, is present in soldiers of the symmetrical snappers (Krishna et al ., ; Rocha, ).…”

Anatomy of the frontal gland and ultramorphology of the frontal tube in the soldier caste of species of Nasutitermitinae (Isoptera, Termitidae)

“…Nevertheless, Quennedey (1984) found only four larger hairs surrounding the frontal pore of Trinervitermes, such as the ones described in the present study for Velocitermes. Campaniform sensilla have already been described on the labrum of some soldiers of the family Rhinotermitidae and on the frontal tube of Spinitermes brevicornutus and Embiratermes festeivellus (Costa-Leonardo and Barsotti, 1996). According to Deligne et al (1981), both the sensory hairs and the sensilla must provide data concerning the distortion of the integumental cuticle when the soldiers are in contact with enemies, thus playing a role in mechanoreception.…”

“…In these soldiers, known as nasutes, there is a rostrum that arises as a prolongation of the insect's head capsule. This nose might vary from a shallow cone open to a long tube, which corresponds to the frontal tube and has the function of expelling the secretion produced by the frontal gland (Costa-Leonardo, 1998, 2001Costa-Leonardo and Barsotti, 1996;Costa-Leonardo and De Salvo, 1987;Fontes, 1987). According to Kriston et al (1977), the soldier caste in the subfamily Nasutitermitinae is always peculiar and different from the other individuals of the colony, so much so that for Deligne et al (1981), this caste is the most specialized among all the castes of social insects.…”