Development, swarming, colony orphaning and fly parasitism in subterranean termites, macrotermes gilvlls (hagen) and macrotermes carbonarius (hagen) (blattodea: termitidae)

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Date
2010
Authors
Kok Boon, Neoh
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Biological and ecological aspects of Macrotermes gilvus (Hagen) and Macrotermes carbonarius (Hagen) namely: (1) the caste development; (2) flight phenologies and reproductive isolation mechanisms; (3) the impact of orphaning in field colonies; (4) fly larva parasitism in both species were focused in this study. The present research provides insight into termite's caste developmental pathways, population biology, colony breeding structures and community ecology. There were three larval instars and five nymphal instars detected in the development of minor/major workers and reproductive castes of both species. The first larval instars consisted of both males and females that displayed homogenous sizes. Size sexual dimorphism, in which females were smaller than males, occurred in second larval instars, third larval instars, and worker castes. Minor and major soldiers were sterile females. Pictorial evidence of fourth larval instar of M carbonarius is presented herein; the individuals closely resembled those of minor workers but were poorly pigmented, having a distended abdomen, future presoldier-like mandibles, and a meso- and metanotum. Chronological reproductive isolation W'lS displayed in two sympatric specIes. Flights of M. gilvus were recorded over a remarkably long 7-month period from March to September, while swarming of M carbonarius took place from November to January. Swarming events of M gilvus and M carbonarius occurred under atmospheric pressures of 1,005-1,011 hPa and 1,006-1,010 hPa, respectively. Most flights of M gilvus occurred on days with rain at dawn (0300-0430 hour), whereas M carbonarius avoided rain at dusk (1900-1910). Flight activity of M gilvus was correlated significantly with atmospheric pressure and rainfall. The threshold temperature and relative humidity (RH) of M gilvus flights were between 23 and 26°C and 83 and 98% RH; M carbonarius swarmed between 25 and 30°C and 72 and 83% RH. Of the 38 orphaned colonies of M gilvus, 15 colonies (39.5%) re-established. In M carbonarius, three colonies out of20 (15%) re-established. Re-established colonies were headed by normal adultoids. In naturally-orphaned colonies of M gilvus, multiple adultoids with normal pigmentation but tom wings were found. The number of reproductives probably declines over time. It may take alates of M. gilvus six months to develop to functional adultoids, and up to 12 months for alates of M. carbonarius. The presence of sexual castes at the time of orphaning may not necessarily guarantee the success of colonies in re-establishing themselves as breeding colonies. A high prevalence of occupation of the mounds by other termite species was found, after the death of M gilvus (18.4%) or M carbonarius (30.0%) colonies. Soldiers with abnormal round head capsule and small mandibles were found in orphaned colonies. A new fly species Misotermes mindeni Disney & Neoh (Diptera: Phoridae), as identified infecting the soldiers of Macrotermes gilvus (Hagen). While the Orientai Bengaliinae blow fly, Verticia fasciventris Malloch (Diptera: Calliphoridae) was reported for the first time as an internal parasitoid of the soldiers of Macrotermes carbonarius (Hagen). Both dipteran species demonstrated different approaches in larval pupation while parasitized soldiers were less aggressive compared to healthy soldiers.
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