SECTION II--INSECTS AND THEIR 

 RELATIONSHIP TO LIGHT 



WHAT INSECTS ARE POSITIVELY PHOTOSENSITIVE 



[SUMMARY] 

 P. W. Oman 1 



Consideration is limited to the reaction of insect populations to induced electro- 

 magnetic radiation under natural conditions. The literature review upon which this paper 

 is based is far from exhaustive. 



There appears to be no simple, uncomplicated answer to the question of what insects 

 are attracted to induced light. Whether or not an insect exhibits a positive response de- 

 pends upon various circumstances, some of which concern the insect itself, some of 

 which depend upon its environment, and some that depend upon the nature of the induced 

 light. Several of these factors are to be discussed by others during this seminar. There 

 are thousands of kinds that respond to light, in varying degrees, under certain favorable 

 circumstances. 



Only in a very general way are there correlations between phylogenetic position of 

 a species and the inclination of its representatives to respond to induced light in a posi- 

 tive fashion. Certain order s--Thysanura, Mallophaga, Anoplura, Zoraptera, and Odonata-- 

 apparently lack species that exhibit a positive response. Other order s- -Collembola, 

 Isoptera, Mecoptera, Dermaptera, Psocoptera, Thysanoptera, and Siphonaptera--are 

 composed largely of species that are not positively photosensitive, yet contain some 

 members that are readily attracted. More critical exploration among representatives 

 of these orders, with different types of light, may considerably alter our ideas. 



The bulk of the photopositive species of insects belong to the orders Ephemeroptera, 

 Neuroptera, Orthoptera, Hemiptera, Coleoptera, Trichoptera, Lepidoptera, Diptera, and 

 Hymenoptera. In general, diurnal species are not attracted to induced light. The great 

 majority of the species that show a marked positive response to light are nocturnal, or 

 carry on some function essential to species survival at night or at dusk or dawn. Examples 

 of these essential activities are emergence to the adult stage, mating, oviposition, feed- 

 ing, and dispersal flights. However, numerous nocturnal species are not positively 

 photosensitive. 



Well-known pest species among the Lepidoptera, the adults of which may be attracted 

 to light, are the codling moth, oriental fruit moth, corn earworm, various cutworms, 

 fall armyworm, cabbage looper, European corn borer, pink bollworm, and others. Many 

 respond only to certain wavelengths of light, and most show definite time peaks of 

 nocturnal activity. Lepidopterous families containing numerous photopositive species 

 are Noctuidae, Notodontidae, Sphingidae, Arctiidae, and Geometridae, as well as many 

 Microlepidoptera of various families. 



The Scarabaeidae and Staphylinidae, among the beetles, contain many species that 

 are attracted to light. However, the Japanese beetle, a diurnal scarab, is not so attracted. 

 The Asiatic garden beetle and the European chafer, both introduced scarabs, are strongly 

 attracted to light, although the European chafer apparently responds to induced light 

 secondarily, after being stimulated by decreasing light intensity to swarm for mating 

 purposes. 



formerly Chief, Insect Identification and Parasite Introduction Research ■ Branch, Entomology Research Division, now with 

 Foreign Research and Technical Programs Division, Agricultural Research Service, U.S.D.A. 



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