Caste Differentiation Pathways in the Neotropical TermiteArmitermes holmgreni(Isoptera: Termitidae)

Abstract

The present study investigated the caste differentiation system of Armitermes holmgreni in natural colonies from the Atlantic Forest in northeastern Brazil. Thirteen measurements were made of the termites encountered in three colonies. The morphometric differences among the instars were analyzed using principal component analysis (PCA). The differentiation patterns of the nymphal lineages of A. holmgreni agreed with earlier descriptions of species of the Termitidae family, with one larval instar followed by five nymphal instars and alates. Nymphoid neotenics became differentiated starting at the fourth or fifth nymphal instar. Two larval instars were observed in the apterous lineage before the appearance of workers, presoldiers, and soldiers. Both workers and soldiers had only one instar each. The A. holmgreni workers consisted of male and female individuals, without sexual dimorphism, a situation that had not been previously recognized among the Syntermitinae. The A. holmgreni soldiers consisted only of female individuals, a pattern observed in most species of Termitinae and Macrotermitinae. The differentiation of nymphoid neotenics starting at the fourth or fifth nymphal instar has also been reported for Armitermes euamignathus. The general patterns of differentiation of A. holmgreni were similar to those previously observed in other species of Syntermitinae.

Unrelated secondary reproductives in the neotropical termite Silvestritermes euamignathus (Isoptera: Termitidae)

“…Multiple secondary reproductives were also found by Barbosa et al (2012) in a nest of Silvestritermes holmgreni without the primaries, suggesting that the occurrence of replacement reproductives may be widespread in the genus Silvestritermes. The female nymphoids of S. holmgreni also varied in size, and these differences were based on the instar of the nymph that differentiated into neotenics (Barbosa et al 2012). Different degrees of physogastry were also found within female neotenics in S. euamignathus, which seem to be associated with the nymphal instar that differentiated into neotenics (Costa-Leonardo et al 1999, Haifig et al, unpublished).…”

Caste differentiation pathways in the Neotropical termite Silvestritermes euamignathus (Isoptera: Termitidae)

“…Monomorphic workers without sexual dimorphism were also observed for S. holmgreni by Barbosa et al . (), but have never been observed in other species of the subfamily Syntermitinae. The worker caste was monomorphic, but considered to be composed of several successive instars according to the traditional concept by Noirot (): in the family Termitidae, the number of instars of workers tends to decrease in the evolutionary process, as well as the morphological differences among the subsequent instars.…”

“…The obvious difference between soldiers and workers was that all the soldiers were female, which was also observed for S. holmgreni (Barbosa et al . ). Unisexual soldiers are common in termites.…”

“…In S. holmgreni , nymphoid neotenics develop from the fourth and fifth nymphal instars (Barbosa et al . ). On the other hand, the nymphoids in S. euamignathus derive predominantly from the fourth instar nymphs, possibly from the third and fifth instars as well.…”

“…Male and female nymphoid neotenics were also observed in the termite Silvestritermes holmgreni (Snyder, 1926) (Barbosa et al . ). This species shares many characteristics with S. euamignathus , including variation in soldier size, which prevents precise identification of these species, and their geographic distribution (Rocha et al .…”