A Re-Examination of the Development of Castes in Mastotermes Darwiniensis Froggatt (Isoptera).

Abstract

The developmental pathways in mature field colonies of Mastotermes darwiniensis are morphologically distinguishable after the moult to the second instar. One pathway leads through a total of six larval stages to the first worker stage. Later stage workers can moult to presoldiers or neotenics. The second pathway leads through 11 reproductive nymphal stages to the alate. The larvae and early workers in field colonies are smaller than those of the same instar in incipient colonies; the instar is best judged from antenna1 segmentation. Workers may continue to moult indefinitely without differentiating. Soldiers in field colonies can develop from workers of an age equivalent to 2 years in laboratory culture at 32ºC, and neotenics after the equivalent of approximately 18 months. Larvae are short-haired, but the first eight nymphal stages bear dense, long hair. The nymphal integument becomes pale brown by the sixth stage; wing buds are evident in the fourth nymphal stage. Eye pigment first appears in sixth-stage nymphs. The ninth and later stages have whitish integument and short hair. The alate has sparse, short hair, but the neotenic is long-haired; the integument of both is pitted. The working caste of Mastotermes is not pseudergate, nor are those of many other lower termites, including some kalotermitids; the working castes of lower termites should be referred to as workers.