398 JVilliam Morton Wheeler 



were obtained. The experiment therefore, throws no Hght on the 

 question with which we are here concerned. 



Much more important are the results of experiments per- 

 formed by Oudemans, Kellogg, Meisenheimer and Regen in cas- 

 trating larvae. 



Oudemans ('99) was the first to attempt surgical castration in 

 insects. He remioved one or both gonads from male and female 

 caterpillars of the gypsy m.oth (Ocneria dispar) before the last 

 and second last m.oults. About one-third of the caterpillars (30 

 out of 86) survived the operation and produced moths. From a 

 study of these, the Dutch investigator concluded that castration 

 has no influence, either on the external appearance, i.e., on the 

 secondary sexual characters, or on the behavior of the moths, 

 since the castrated males copulated, though they had no sperma- 

 tozoa, and the females, though they had no eggs, nevertheless 

 stripped from their abdomens the mass of long hairs in which 

 they normally oviposit. Females castrated only on one side laid 

 eggs, and three normal females thatcopula ted with castrated males, 

 laid eggs which developed parthenogenetically. 



Kellogg ('04) succeeded in castrating silk-worm caterpillars 

 (Bombyx mori) after the second, third and fourth moults by burn- 

 ing out the gonads with a hot needle. This method was very 

 inferior to that employed by Oudemans. Not only was the mortal- 

 ity of the caterpillars greater, to judge from Kellogg's remarks, 

 but the complete destruction of the gonads was obviously much 

 less certain. Like Oudemans, he failed to detect any modifica- 

 tions of the secondary characters of either sex in cases in which 

 dissection of the adult moths proved that the gonads had been 

 completely destroyed. 



More recently Meisenheimer ('07) has carried out much more 

 elaborate experiments than either of his predecessors, on about 

 600 Ocneria dispar caterpillars, of which 186 yielded imagines. 

 The smallest caterpillars castrated were between the second and 

 third moults, and about | cm. long, but he also used those be- 

 tween the third and fourth and between the fourth and fifth 

 moults. He was able to remove the gonads even before the second 

 moult but the larvae were too delicate to survive the operation. 



