NO. lO TROPISMS OF LEPIDOPTERA MclNlXJO I5 



living insect, which when laid upon a photographic plate leaves an 

 impression, plays no part in this attraction. 



Loeb (43, p. 155) in 1889 seems to have been the first one to use 

 the term chemotropism in connection with the responses of Lepi- 

 doptera that have just been discussed and with the attractiveness which 

 meat has for blowflies and their larvae. 



As the writer (54, 55) has recently reviewed the literature dealing 

 with chemotaxis in economic entomology, only a short discussion need 

 be given here. 



Chemotaxis, like the other tropisms, has two divisions. Attrahents, 

 usually called " attractants," induce positive chemotaxis and repellents 

 induce negative chemotaxis. For our purpose here Tragardh's (85) 

 definition will suffice. He says (p. 113) : 



By the term " chemotropism " is meant, as well known, the automatic orien- 

 tation of the animals to any olfactory sensation in such a manner that both sides 

 of the body are struck by the lines of diffusion at the same angle. Theoretically, 

 when a substance diffuses an odour, fine particles are ejected in straight lines, 

 but in reality the air currents cause the Ijnes to deviate from their straight track. 



In the control of Lepidoptera many practical applications of chemo- 

 taxis have been made. Attractive poisoned bran baits are used as 

 control measures against armyworms and cutworms. As early as 1896 

 baited traps were used by collectors to catch large numbers of fer- 

 tilized, egg-laying female moths. Many years ago the common control 

 method against grapevine moths in Europe was the use of attractive 

 baits ; but more recently the use of insecticides has supplanted this 

 method as a control measure, so that now it seems to be used only as 

 an indicator of the approximate number of moths present. With this 

 information the grower knows when to apply the insecticides. 



A molasses-yeast bait was placed by Peterson {72) in a peach 

 orchard in New Jersey, and it was observed that large numbers of the 

 oriental fruit moth came to the bait pans. This observation was a 

 stimulus for more extended work with attractive baits, but this par- 

 ticular bait when fermenting proved to be the most attractive one 

 tested. Frost (24) used weak acids, volatile oils or their constituents, 

 sugars, and molasses as attractants. The fermenting sugar baits 

 attracted the most moths. Peterson (73) tested about 250 aromatic 

 chemicals as possible attractants for the oriental fruit moth. Terpineol 

 and several essential oils were somewhat attractive, but not so attractive 

 as several fermenting sugar-producing products. Fermenting fruits 

 (dried fruit in water), particularly prunes, pears, and apricots, at- 

 tracted large numbers of moths. By using dried fruits, sugars, and 



