48 DIAMOND-BACK MOTH. 



Mr. de Witt Meulen also mentioned that the larvae 

 collected by him in the beginning of August, that is 

 in the S. African winter (corresponding in time of year 

 with the height of summer here), did not develop into 

 moths, but " gnats " only (Ichneumon flies, from which 

 it would appear that this attack must be much kept 

 down by parasites, S. D. B.) appeared instead. The June 

 and August presence of caterpillars would correspond 

 with that of the first and second brood in Germany, 

 which are thus described by Dr. E. L. Taschenberg : 



" The sixteen-footed caterpillars are attenuated at 

 each end, of a bright green, and sprinkled with small 

 bristles, but of which the wart-like bases can only be 

 seen when much magnified. The head is black. 

 Length, 7 mm. At the beginning of June ; for the 

 second time in August and September, under a thin web 

 at the back of the leaves of many different kinds of 

 plants of the cabbage tribe, both wild and cultivated."* 



Specimens of cocoons containing the chrysalids were 

 needed to complete the S. African set ; but from the 

 identity of the species and similarity of its habits, in 

 all that was reported, with those of the Diamond-back 

 Moth of Europe (Fig. 21, p. 47), it may be presumed 

 also that the caterpillar goes into chrysalis, as in Europe, 

 in a cocoon spun on the food-plant or on the ground. 



For prevention of attack, if it is practicable as men- 

 tioned by Mr. de Witt Meulen to place sticky material 

 so as to trap the moths, this would of course be 

 desirable; also where a crop has been destroyed, or 

 weeds near a crop are much infested, it would be well to 

 collect the injured remains before the moths came out 

 of the chrysalids and destroy them. Burning of course 

 would be the surest way, but, as it is the nature of the 

 chrysalis to go through its changes in a more or less 

 open web exposed to air and changes of weather, 

 probably ploughing in of the infested remains would 

 be sufficient treatment, if done before the moths developed. 



* See 'Praktische Insekten Kunde,' by Dr. E. L. Taschenberg, pt.III. 

 p. 273. 



