Comparative ultrastructure of the scale cover of three aspidiotus spp. (Hemiptera: Diaspididae) and the ovipositor of their two parasitoids usign scanning electron microscopy

Correct identification of both the target insect pests and their natural enemies is important in biological control management programs. In the recent coconut scale insect (CSI) outbreak in the Philippines, misidentification of the destructive pest population resulted to an unsuccessful biological control application. The present study aims to examine scale cover of three Aspidiotus species previously reported in the Philippines, the CSI species - A. destructor Signoret and A. rigidus Reyne, including the oleander scale A. nerii Bouche at higher magnification using scanning electron microscopy (SEM) to validate the difference in scale cover thickness reported in previous literatures. SEM observations revealed that A. destructor Sign. and A. rigidus Reyne scale cover are similar ultrastructurally. A multivariate analysis of covariance indicates no significant difference between the thickness of the three Aspidiotus spp. along five points in the mid-section of the scale cover while controlling scale cover length as covariance (Pillais Trace = 0.980; p-value = 0.789 \u3e 0.05). Additionally, a comparative observation of the ovipositor of the hymenopteran parasitoids directly associated with the two CSI species was done to provide structural evidence that links ovipositor structure to host specificity. The aphelinid wasp Aphytis lingnanensis Compere parasitizing A. destructor Sign. is an ectoparasitoid was observed to have a very sharp and slender ovipositor with a simple pointed tip which is suitable to avoid puncturing or drilling through the fragile cuticle of its host. The encyrtid wasp C. calauanica Barrion, Almarinez & Amalin is an endoparasitoid with a characteristically pointed but strongly dented, with serrated distal teeth useful for drilling through the integument of the host. The structure of the ovipositor tip of the hymenopteran parasitoids directly associated with the two CSI species examined under SEM are congruent with their mode of parasitization