Larval head morphology and ultrastructure of sensilla in tyrannophagous Mythimna separata and Spodoptera litura
Both Mythimna separata and Spodoptera litura larvae are polyphagous and gluttonous,posing a serious threat to the safety of food crops and other cash crops in China.The present study systematically observed and described the head morphology,antennae,and sensilla on the mouthparts of M.separata and S.litura from the 3rd to 6th instar larvae using a scanning electron microscope(SEM).The results showed that the head of M.separata larvae was subrounded,while the head of SS.litura larvae was ellipsoid.Four types of sensilla-sensilla trichodea(St),Sensilla chaetica(Sc),Sensilla basiconica(Sb),and Sensilla styloconica(Ss)were distributed on the antennae of these two species.Three types of sensilla:Sensilla chaetica,Sensilla basiconica,and Sensilla styloconica were distributed on the maxilla and labium,with two subtypes of Sensilla chaetica and Sensilla basiconica.With increasing instar,the types of sensorium sensilla and morphological characteristics of the head of M.separata and S.litura larvae remained unchanged,but the length and basal diameter increased to different extents,and these two larvae of the same instar differed somewhat in sensilla size.In terms of sensilla number,Sensilla basiconica type Ⅰ(Sb Ⅰ)of M.separata larval maxilla increased significantly with increasing instar,reaching a maximum at the gluttonous stage,but this phenomenon was not observed in SS.litura.This result may provide an ultrastructure morphological basis for investigating the differences in host plant selection between these two gluttonous pests.
Mythimna separataSpodoptera liturasensilla of larvascanning electron microscopygluttonous stage
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