Study On The Ecological Effects Of Invasion By Sphaeroderma Apicale (Baly)

Basing on the method of system analysis, we studied the structure and dynamics of arthropod communities in cornfield in the western Hubei province invaded by Sphaeroderma apicale Baly. The results were shown as below.1 Field investigations and laboratory observations were conducted to characterize the Sphaeroderma apicale Baly in biological and ecological aspects. The results revealed the developmental duration and morphological characteristics of the species in each developmental stage as well as the its occurrence dynamics in the cornfield of mountainous areas of western Hubei province, China. The discovery can contribute theoretically to the establishment of IPM against the Sphaeroderma apicale Baly.2 The post-invasionary habitation of Sphaeroderma apicale Baly affected the native arthropod community by reduction of richness (68 species), evenness (0.46) and diversity (1.79), elevation of concentration, and predomination of Sphaeroderma apicale Baly with 0.40 in domiance compared with 0.33 for corn aphids. The change of the indexes indicates that the invasion of Sphaeroderma apicale Baly reduced the diversity and unstabilize the arthropod community from original situation, therefore the maintenance of the natural enemies' regulation should be highlighted.3 Spatial and temporal quantification of nich overlap and nich breadth were employed to analyze the change of pest insects and their natural enemies in the two kinds of different cornfields. The Sphaeroderma apicale Baly replaced corn aphids as predominant insect pest in the cornfield after its invasion. Neoscona theisi occupied the broadest temporal niche among the natural enemies, followed by Erigonidium graminicolum, Misumenopos tricuspidata, Coccinella septempunctata(L.), Propylae ajaponica Thurbery, Leis azyridis Pallas, Scymnus quadrivulneratus Mulsant, Chrysopa septempunctata, and Ommatius chinensis in descendant order. The niche of Sphaeroderma apicale Baly overlapped largely with Neoscona theisi and Erigonidium graminicolum both in temporal and spatial axis. Coccinella septempunctata (L.) and Chrysopa septempunctata were next to them whereas rest natural enemies had insignificant overlap with Sphaeroderma...