THE OVIPOSITION RESPONSE OF INSECTS 13 



throws considerable light upon it. 7 Craighead finds that nearly all 

 adult cerambycids display a marked preference for the host wood 

 in which the} T have fed as larvae, and that certain species which can 

 be induced to feed in a new host show a preference for that host 

 when they become adults. Concerning oviposition, lie says (14- V- 

 220) : 



Although the adults show a decided predilection for a favored host in 

 ovipositing and even, in certain species, a preference for the plants in which 

 the larva? have fed for one or two generations, the instinct to oviposit seems 

 to overbalance that of host selection, consequently new hosts ai*e frequently 

 selected — possibly more frequently in nature than is generally realized. 



If it can be sliown that the food of the larva determines the host 

 preference of the adult, a decided step in advance will have been 

 made. Another step then will be to explain whether the " memory ?1 

 of the food plant which the larva lias passed on to the adult is the 

 result of or is influenced by the chemical or physical effects of 

 the food in the growing larva. 



CONCLUSIONS 



The following internal factors may condition the oviposition 

 responses of insects : The nutritive state as affected by the amount 

 and chemical constitution of the food, age, fertility, and internal 

 stimuli which determine periodic egg-laying. 



The external influences which may affect the oviposition response 

 are temperature, humidity, light (including color), air currents (and 

 probably in some species water currents), the physical character of 

 surfaces, the chemical constitution of substances which stimulate on 

 contact, and the volatile constituents of substances. 



The simplest oviposition responses are probably shown by insects 

 which spend most of their lives upon substances that serve as food 

 for themselves and their offspring. 



Most free-living insects, however, require a** chain of stimuli to 

 provoke egg laying: a single stimulus is insufficient to call forth a 

 normal response. Many species demand a specific chain of stimuli. 



The odor of a substance may attract gravid female insects, but is 

 probably never in itself sufficient to induce normal oviposition. 



LITERATURE CITED 



1 1 > Adolph, Edwabd F. 



1920. Egg-laying reactions in the pomace fly, Drosophila. In .Tours Bxpt. 

 Zool., vol. :u. pp. 327-341. 

 (2) Bachmetjew, P. 



1907. BxperSmentelle entomologische Stuclien. vol. :i, xvi+9444-cviii 

 pp., 31 figs., Sophia. 

 C!i Hack, E. A., and PembeRtOn, C. 15. 



1914. Life history of the melon fly. In Jour. Agr. Research, vol. .*5, 

 pp. 269-274. 



(4) Baiixon, P. Cappe de. 



1920. Contribution auatomiQue el physiologique a l'etude de In repro- 

 duction chez les locustiens e1 les grilloniens, I. i.m ponte el 

 IVjelosion chez Its locustiens. fn La Cellule, vol. 31, pp. 1 245. 



(5) Barrows, Wii.i.i \.m Morton. 



1D07. The reactions of the pomace fly, Dro»ophHa mnpelophila Loew, o> 

 odorous substances, tn .lour. Expt. Zool., vol. 4, pp. - r »h" 537. 



■ An Imnortanl di. < u --'u,n b Bnie ol rhl* and -imihir <• ■!.-■ lias recently appeared (cf. 

 Wat., vol. 58, pp. 127 1 1 1. Id24). 



