Observation on the external morphology and ultrastructure of compound eyes of adult Agrotis ipsilon (Lepidoptera: Noctuidae)

Agrotis ipsilon is a widely distributed migratory pest, which causes severe damage to maize and other important crops. By analyzing the structural characteristics of the compound eye, we can understand the relationship between the complex visual behavior and the mechanism of photosensitivity and phototaxis of A.ipsilon.

Optical microscopy, scanning electron microscopy and transmission electron microscopy were used to observe the external morphology and internal ultrastructure of the compound eyes of A.ipsilon adults.

The results showed that the compound eyes of A.ipsilon adults were symmetrical compound eyes, born at the base of head antennae, and ellipsoidal in shape. The areas of compound eye in female and male adults were (1.646 ± 0.046) mm² and (1.554 ± 0.063) mm². The compound eyes of females and males had (4 679 ± 131) and (4 398 ± 170) ommatidia per eye, respectively. Most of the ommatidia were regular hexagonal, and a few were pentagonal. The surface of each ommatidium was densely covered with corneal nipples, and there were occasional interfacetal hairs in the gap. Each ommatidium was composed of one cornea, four crystalline cone cells, one pair of primary pigment cells, six secondary pigment cells, eight retinal cells, and a basement membrane. The compound eyes of A. ipsilon adults were of the typical superposition type. The distribution pattern of rhabdom followed the '7+1'. There were no obvious differences in the arrangement and internal structure of ommatidia between the female and male adults, but compound eye area and the number of ommatidia in females and males presented obvious sex dimorphism.

This study provided a theoretical basis for the monitoring and control of A. ipsilon using phototaxis.