Ent. exp. & appl. 13 (1970): 359--361. North-Hol land Publishing Co., Amsterdam

SHORT COMM UNICATION

ELECTROPHYSIOLOGICAL RESPONSES TO LIGHT IN THE

C O M P O U N D EYES OF SOME S T O R E D - P R O D U C T INSECTS

BY

U R I Y 1 N O N *

Vision Research Laboratory, Hadassah Hospital, and Dept. of Entomology Hebrew University, Jerusalem, Israel

Tha t stored-product insects demonstrate behavioral response to light is well-known (Stermer, 1959; Sohi, 1966; Yinon & Shulov, 1966). The question asked is whether these insects, which exist always in conditions of low il lumination or darkness, possess a normal visual mechanism. In order to clarify this, electroretinograms have been recorded from the compound eyes of the adults of the yellow mealworm beetle Tenebrio molitor L., the hide beetle Dermestes maculatus De G., and the khapra beetle Trogoderma granarium Everts. Nineteen specimens were the subject of experiments in T. molitor and four in each of the other species.

Conventional optical and electronic equipment were used to stimulate the eyes and to record the response (Yinon & Auerbach, 1969). A computer of average transients was used and permitted accurate diagnosis of the response pattern. Fifty responses for each stimulus type (i.e., l ight intensity) were averaged. A dark adaptat ion of 5 - -10 minutes was given before each experiment.

The results showed that a similar wave-form of the electroretinogram response was received f rom each of the above-mentioned species (Fig. 1). The E RG is composed of a negative and fast potential followed by a second one which is positive and slow. The amplitude was reduced and the latent period was elongated with a reduction in the intensity (Fig. 2). The min imum intensity needed to elicit response in T. granarium was - -0 .8 log units whereas in T. molitor it was - -1 .6 , and - - 2 . 4 in D. macut.atus. Presumably this indicates a different threshold sensitivity for each species. There were considerable variations between the species in the latent periods and in their response/ intensi ty curves.

With respect to the electrical activity of the stimulated compound eye of adult stored-product insects, they have certain functions in common with other insects tha t have normal visual activity (Mazokhin-Porshnyakov, 1969).

Thanks are due to Professor E. Auerbach, in whose laboratory the experiments were conducted.

* Present address: Depar tment of Ophthalmology, Duke University Medical Center, Dur- ham, Nor th Carol ina 27706 U.S.A.

Fig

. 1.

The

ER

G (

elec

tror

etin

ogra

m)

of s

tore

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oduc

t be

etle

s. T

he s

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as 2

8 m

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and

ligh

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itie

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0 (=

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--

1.6,

an

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2.4

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ed.

Fif

ty

resp

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s w

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ity-

stim

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rom

th

e to

p.

SHORT COMMUNICATION 361

mV 20

Oermestes 16

12 -

8

4

0 Trogoderma

16 -

12 -

IC- 4 -

0 ~ o Tenebrio

16 -

I V

8 -

4 - -

0 -0.8 -1.6 -2.4

O--

m s e r

200

160

120

80

40

0

160

120

80

40

0

160

120

80

40

0

Dermestes -

Trogoderma

- C-

I

Tenebrio

Log I _ _ I _ _ L _ _ _ _ L _ Log I 0 -0.8 -1.6 -2.4

Fig. 2. Amplitude (mV) and latency (msec) changes in the negative potential of the ERG as a function of stimulus intensity.

REFERENCES

MAZOKHIN-PORSHNYAKOV, G .A. (1969). Insect Vision, Plenum Press, New York. SOHI, G. S. (1966). Response of the larvae of Trogoderma granarium Everts (Dermestidae:

Coleoptera) to different types of light. Ind. l . Agric. Res. Punjab 3 : 166--173. STERMER, R. A. (1959). Spectral response of certain stored-product insects to electromagnetic

radiation. J. econ. Entomol. 52 : 888--892. YINON, U. & AUERBACH, E. (1969). The visual mechanisms of Tenebrio molitor: Variations

taking place in the E R G of pupa and adult during development. J. exp. Biol. 51: 635--641. YrNON, U. & SUULOV, A. (1966). Spectral discriminative ability of larvae of Trogoderma

granarium Everts. Ent. exp. & appl. 9 : 256---270.