Changes in Morphological Traits of Aphis Craccivora Koch (Hemiptera: Aphididae) in Relation to Different Host Plants of Family Fabaceae

Aphids are soft bodied sap sucking insect which cause great damage to agricultural and horticultural plants. Aphids have undergone several morphological and physiological changes in order to live on different host plants. The various host plants act as agents of natural selection. Therefore, morphology may reflect host specific behavioral adaptation. The morphological characters of Aphis craccivora was examined on four host plants viz., Phaseolus sinensis, Lablab purpureus, Vigna radiata and Vigna mungo. The results indicated that host plants have a significant effect on morphological traits of A. craccivora. All the morphological characters viz., body length, width, antennal length, ultimate rostrum segment, hind tarsus, siphunculi, and cauda were investigated. The maximum growth (length and width) of alate and apterous was observed on P. sinensis (2.19±0.10, 1.18± 0.01 and 1.98±0.04, 1.32±0.01) followed by L. purpureus, V. radiata and V. mungo. The significant variation is observed by t- test (t=0.06 and 0.12 P<0.05). Similarly, the maximum body size of instars stages were also observed on P. sinensis and minimum on V. mungo. The variation is obtained highly significant by Anova test for length and breadth (F1=189.43, F2=16.04; P<0.05 and F1=30.65, F2=325.08; P<0.05). The number of antennal segments, length of hind tibia, siphunculi, cauda and number of caudal hairs are found to be useful characters for identifying instars stages. The maximum size of aphis was observed on P. sinensis and minimum on V. mungo. It is probably due to chemical substances and presence of trichomes on leaves which reduced phloem feeding activities of aphids.