MSc

The taxonomy of weevils under the subfamily Rhynchophorinae (Coleoptera:
Dryophthoridae) was carried at the College of Agriculture Padannakkad, Kasargod,
Kerala and seven different agro ecological zones of Kerala during 2014-2016.
Study was based on survey carried out in agro and forest ecosystems of Kerala and
the samples collected from these ecosystems. Commercially available pheromone
traps for the collection of red palm weevil, banana pseudostem weevil and banana
rhizome weevil were installed in five agroclimatic regions viz., Northern Zone,
(RARS, Pilicode); High range (RARS, Ambalavayal); Central Zone (RARS,
Pattambi); Problem zone (RARS, Kumarakom) and Southern Zone (RARS,
Vellayani). Traps were also installed in the fields of BRS, Kannara and ORARS,
Kayamkulam. The other two weevils, i.e. Diocalandra frumenti and Sitophilus
oryzae were collected from households and fields of the aforesaid seven regions.
The study also includes specimen stored in Malabar Insect Repository (MIR) and
the specimens of Rhynchophorus ferrugineus collected from CPCRI regional
station, Kayamkulam, Kerala.
An annotated checklist of world Rhynchophorinae was prepared and results
revealed that the subfamily Rhynchophorinae includes 955 species under 124
genera and 6 tribes. The distribution of these weevils is more concentrated in
Oriental and Neotropical regions (70%). Maximum number of species was
described during the 1851-1950. Highest contribution from coleopterists was by
Heller (89 species) followed by Chevrolat (76 species), Faust (76 species),
Guenther (68 species).
Taxonomy ultimately narrowed down to focus on the 770 specimens of five
species under five genera viz., Cosmopolites sordidus, Diocalandra frumenti,
Odoiporus longicollis, Rhynchophorus ferrugineus and Sitophilus oryzae.
Collected specimens of individual species were segregated into different
populations according to the morphological variations within the species. The
present study of economically important five species had 249 illustrations and 149
line diagrams.Detailed description of all the taxonomic characters like head, rostrum,
(dorsal and lateral), antennae, pronotum, elytron, femur, tibia, tarsus, venter and
genitalia were studied and presented with line diagrams. Taxonomic description of
all the five species were supplemented with standard taxonomic terminology along
with genital characters and loaded with the morphometric ratios. The taxonomic
key was prepared for all the known species under genera Cosmopolites,
Diocalandra, Odoiporus and Rhynchophorus.
Based on the morphological characters all five species were segregated in
different groups. The taxonomic study revealed that, morphological variations
present among the groups may be due to environmental conditions, availability of
food, and life stage of the plant on which they are feeding on. All the variations
within the species were depicted with the differential distinguishing characters
along with line diagrams. Among all five species, major difference was observed
within the three groups of Odoiporus longicollis which may be a new species. More
morphological and molecular level studies are needed for the confirmation of new
species if any.