490 



its food, the Bruchid had deposited eggs. Mr. Swezey reported, 

 in 1912, the eggs of Caryoborus deposited on green bananas 

 where they hatched and the young larvae died after eating 

 some way into the skin of the fruit. In one case I saw its 

 eggs densely peppered over the surface of the wooden slats of 

 the shutters of a house. We have, then, in this species a striking- 

 failure of an insect to discriminate in regard to oviposition 

 upon suitable material for the larval food. 



In the case of the Bruchus pruininus I have found the eggs 

 deposited under natural conditions on Ipomoea seeds, on castor 

 beans, and on seeds of Cassia glauca, in none of which the 

 larvae can l)reed, and on indigo seeds wliich give an adult so 

 small as to suggest sexual impotence. In experimental work 

 almost any of the legumes used would be oviposited on without 

 regard to its suitability as larval food. It would not be diffi- 

 cult to assemble many similar cases among other groups of 

 insects. Thus the Mediterranean fruitfly {Ceratitis capitata) 

 seems particularly fond of ovipositing in the rough-skinned 

 lemon locally common in Honolulu though ordinarily none of 

 the larvae produced can mature. Mr. Pemberton has found that 

 in ca])tivity the Opiine parasites, Opius humilis, Diacliasma 

 trijonl, and D. fullawayi, readily oviposit in the melon fly 

 (Bactroccra cucurhitae) though entirely unable to develop 

 there. Mr. Timberlake has observed Dinocampus terminatus 

 ovipositing in Coccinelids in which they fail of development. 

 Such "failures of instinct" to employ an old-fashioned terui 

 might be dismissed as "'imperfect adaptations," but they seem 

 worthy of some consideration since they seem to me to be of 

 some importance in the economy of the species. 



I take it that oviposition is an act resulting from several 

 sensory impulses acting together upon the female in a state of 

 nervous tension owing to the presence in her body of eggs 

 ready for laying. These external stimuli may be tactile, 

 visual, or olfactory or they may be compounded of these and 

 other factors. Oviposition then is a complex reflex and will 

 take place whether the material encountered is suitable for 



