Abstract
The present study was carried out to trace the life cycle of mealy bug, Rhizoecus amorphophalli on three different hosts including elephant foot yam, taro and tannia tubers. Investigation revealed that the mealy bug reproduces sexually and the adult female secretes an egg sac of white waxy substance in which eggs were laid. Female nymph moult normally, but male instar produces a cottony puparium around its body and form a pupal stage from which adult males emerge. On tubers of elephant foot yam, average fecundity and incubation period were 68.30±6.22 and 7.80±0.88 days respectively. But, it was significantly lesser for those on the taro and tannia tubers. Nevertheless irrespective of hosts, the percentage of hatching maintained uniformity. The total life cycle of bug which includes three instars and a pupal stage took 27.10 days for females and 22.40 days for males on tubers of elephant foot yam. The larval stages of mealy bug did not show prominent morphometric changes among the hosts used for life cycle study. Key words: Rhizoecus amorphophalli, elephant foot yam, taro, tannia, mealy bug, biology, life cycle. 
Highlights
Among the insect pest complex in agricultural ecosystem, mealy bugs (Hemiptera: Pseudococcidae) have ever been rated as a major pest, since they play a dual role as pest and vector in field crops
During the last few decades, the mealy bug, Rhizoecus amorphophalli Betrem has emerged as a noxious pest infesting on stored tubers of elephant foot yam, taro and tannia (Palaniswami and Pillai, 1979; Rajamma et al, 2002, 2006)
The nucleus culture of R. amorphophalli was obtained from the pure culture maintained on the tubers of elephant foot yam at the Biopesticide laboratory of Central Tuber Crops Research Institute (CTCRI), Thiruvananthapuram and from the mealy bug infested tubers of elephant foot yam, taro and tannia collected from the field of CTCRI at harvest
Summary
Among the insect pest complex in agricultural ecosystem, mealy bugs (Hemiptera: Pseudococcidae) have ever been rated as a major pest, since they play a dual role as pest and vector in field crops. During the last few decades, the mealy bug, Rhizoecus amorphophalli Betrem has emerged as a noxious pest infesting on stored tubers of elephant foot yam, taro and tannia (Palaniswami and Pillai, 1979; Rajamma et al., 2002, 2006). 15 to 25% starch and fairly good amount of protein and minerals (Moorthy and Padmaja, 1991) with indisputable palatability, medical utility and therapeutic values (Suja et al, 2010) They play a vital role in food security and are the important staple or subsidiary food for a large population (Ramanandam et al, 2008; Quaye et al., 2009). Each stage of this insect was studied in detail with a stereo zoom binocular microscope (Leica M10, Leica Microsystems and Weltzar, Germany, magnification: 12-50 X). Measurements and images of egg and other stages of mealy bugs were taken using Stemi-2000C stereo microscope
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