Yellow-winged grasshoppers (Gastrimargus musicus) were captured in the field to examine the morphology and amine immunohistochemistry of their salivary glands. Fifty-eight grasshoppers were collected, with only five being males. Eight of 53 female grasshoppers had food in their crop, and the salivary glands of those insects were significantly heavier than those of grasshoppers without food in their crops. The salivary gland of the yellow-winged grasshopper was an acinar-type gland, similar to gland descriptions for other Orthoptera. The primary secretory part of acini of each gland is composed of zymogen and parietal cells. Staining patterns indicated that serotonin and dopamine could act as neurotransmitters and/or neurohormones to stimulate the glands. The pattern of staining of serotonin in the salivary gland suggested that serotonin stimulates both zymogen and parietal cells. Only the parietal cells were positively stained with dopamine. Comparing staining of glands of grasshoppers with food in their crop with the glands of grasshoppers with empty crops suggested a reduction in staining for serotonin in the latter. The differential staining pattern suggests that these amines have different roles in the salivary gland of G. musicus. The lack of difference in structure but increased mass with feeding suggests that all glands were active, but that secretion was actively occurring only in animals with the heavier glands.

Abstract. The Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Olivier, 1790) is insect pest to plants of the family Palmaceae. No study has been reported on the digestive mechanism of Red Palm Weevil (RPW). Salivary glands are responsible in the feeding regulation of insect while serotonin and dopamine play a significant role in the regulation of this gland. It is great to see the morphology of the salivary gland and how dopamine and serotonin possibly play their role in this gland. Two variation of RPW, striped and spotted RPW were chosen. The morphology of the gland of both RPW variants examined by using light microscopy was found to be a tubular type. Immunohistochemical analysis conducted showed that serotonin and dopamine in both variations did not innervate the glands suggesting they are not act as neurotransmitter. However, it can be detected on few areas within the glands. This suggests that serotonin and dopamine may act as a hormone because there is no evidence on the nerve fibers. The role of these biogenic amines in the salivary gland of RPW needs further investigation. Hopefully the data would help in understanding the mechanism of salivary glands control by biogenic amines in RPW specifically and insects with sucking mouthpart generally.

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Abstract-Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae) is a very destructive insect pest to plants under the family of Palmacea such as dates palm, coconut tree, sago palm as well as oil palm. Many studies conducted on RPW required large numbers of weevils of various stages, hence rearing is needed to solve the problem. In this study, RPW reared on sugarcane in the laboratory for several generations to facilitate biological studies of this tissue-boring pest. The rearing was conducted at National University of Malaysia, Bangi, Selangor. Adult weevils collected from the field by using pheromone trapping method. The adult weevils supplied with stems of sugarcane for food and they were also oviposited on it. The larvae were fed on stems of sugarcane until pupation. The length and size of the sugarcane stems were propotional to the size of the larva. Data on the duration of developmental life stages were recorded. The larvae fully developed on sugarcane and molted 8 times within the mean of 70 days. The larvae were able to construct cocoons due to the availability of fibers in the sugarcane. Sugarcane is the best diet to be used in the mass laboratory rearing of RPW in Malaysia.