Lumen Anatomy and Localization of Wolbachia Sp. in the Thrips, Plicothrips apicalis (Bagnall)

A detailed anatomical study of digestive system of insects has been done in some of the major insect orders such as Lepidoptera, Diptera, Coleoptera and Hemiptera. For other insects such as thrips, their emergence as an important agricultural pest has brought order Thysanoptera to focus. We describe the alimentary canal of Plicothrips apicalis (Bagnall) (Phlaeothripidae) and localize Wolbachia sp. in P. apicalis. The digestive tract of P. apicalis, a grass feeding species, is observed to be well demarcated in the foregut, midgut and hindgut. We evince a new finding in this study that the midgut opens into a globular chamber containing the mycetome. It is from the globular chamber that the hindgut follows and at their juncture, two pairs of malphigian tubules originate. The presence of mycetome has been reported in order Hemiptera and Isoptera that bears a structure similar to mycetome, known as paunch that harbours protists which are known to be involved in cellulose digestion. Presence of mycetome has not been reported in other thrip species till date except in Bactothrips buffai. The finding of an additional structure in the alimentary canal of thrips is suggestive of the significance it might hold in the evolutionary linking with other insect orders. We also tried localizing endosymbiont in P. apicalis and detected Wolbachia sp. in the abdominal region of both the larva and the adult.