Ultrastructure Of The Head Of Monolepta Hieroglyphica(Motschulsky) And Its Response To Host Volatile Compounds

Monolepta hieroglyphica(Motschulsky)(Coleoptera: Chrysomelidae)is a major destructive agricultural pests of cptton,corn,sorghumand grain.This study focus on the chemical ecological adaptation of M.hieroglyphica to host plant.The components and contents of volatile compounds in cotton and corn were collected and identified by GC-MS,and the electroantennography and "Y" olfactory instrument were used to identify the components and contents of volatile compounds in cotton and corn.The compounds with electrophysiological and behavioral activity to the M.hieroglyphica were screened out,and the main volatile components of the host were identified.Moreover,antenna and mouthparts ultrastructure of M.hieroglyphica were observed under scanning electron microscopy(SEM)to clarify the role of sensilla of antennae and mouthparts in host selection.In order to elucidate the host selection mechanism,the natural active substances were used to control the insect M.hieroglyphica.(1)Ultrastructure of adult head of M.hieroglyphica: Antenna of female and male M.hieroglyphica is linear,and composed of 11 segments.This research found 7 types antennal sensilla,consist of sensilla trichodae 1 and sensilla trichodea 2,sensilla chaetica,sensilla basiconica 1 and sensilla basiconica 2,sensilla campullacea and B?hm bristles.Among the 7types of sensilla,the number of Sensilla teichodae 1 is the most,and the quantity of Sensilla chaetica is less.The mouthparts of mature larva and adults are belong to chewing mouthparts.There is a significant difference in maxillary palps and labial palps: the maxillary palps of larvae are only three segmented,and the labial palps have two segments.The mouthpart has 5types sensiila,consists of sensilla trichodae,epipharyngeal sensilla,leaf-shaped setae,sensilla chaetica,and sensilla basiconica.In addition,leaf-shaped setae is not observed in the mouthparts of mature larvae.(2)Composition and daily rhythm of volatile compounds of cotton and corn: the total of40 compounds were detected in healthy cotton leaves,mainly terpenes,lipids,alcohols,ketones,acids etc.After the damage cotton leaves at 6h,18 h,24h,36 h,48h,a total of 32、35、36、44、26 compounds were collected respectively.Compared with healthy cotton leaves,the changes of volatile compounds of terpenes and aldehydes in pest leaves were more obvious.Among them,D-Limonene,β-Santalene,Elixene,(E)-β-Farnesene,Pentadecanal,(E)-2-Hexenal etc.are newly developed compounds,γ-Terpinene,3-Carene,1-Caryophyllene,β-Ionone and(+)-α-Longipinene have disappeared after pests.The total of 29 compounds were detected in healthy corn leaves,mainly terpenoids,aldehydes,lipids,alcohols etc.After the damage corn leaves at 6h,18 h,24h,36 h,48h,a total of 32、32、33、37、26 compounds were collected respectively.Compared with healthy maize leaves,the species of compoundschanged significantly after pest,among which terpenes,aldehydes and alcohols were different.β-Pinene,β-Myrcene,Humulene,β-Santalene,γ-Bisabolene,Nerolidol,β-Bisabolol,(E)-2-Hexenal are newly developed compounds,1-Caryophyllene,7-Tetradecen,Phytol,Diisobutyl phthalate have disappeared after pests.(3)The EAG and behavioural response results of M.hieroglyphica to volatiles: the most significant EAG responses of M.hieroglyphica males and females were elicited by 10 μg·m L-1and 1 μg·m L-1 of γ-terpinene,10 μg·m L-1 of D-limonene,and 10 μg·m L-1 of β-Ionone,followed by 10 μg·m L-1 and 10-2 μg·m L-1 of α-caryophyllene,and 10 μg·m L-1,1 μg·m L-1 and10-2 μg·m L-1 of caryophyllene oxide.Both males and females had a lower response to odecane and tridecane.The results of Y-shaped olfactometer bioassays indicate that females were attracted by 10 μg/m L of β-Ionone,but were repelled by γ-terpinene and caryophyllene oxide.Males were attracted by γ-terpinene and D-limonene but repulsed by β-ionone.