6 BULLETIN- 1016, L\ S. DEPARTMENT OF AGEICULTURE. 



that the Larvse marooned on this leaf, unable to seek their usual pu- 

 pation qua,rters, were forced to enter the petiole. 



From laboratory experiments it was found that when placed in 

 water the larvae, especially those nearly mature, were sustained on 

 the surface film and were able to make considerable progress by lat- 

 eral contortions. When once fully submerged, however, they were 

 unable to regain the surface. Larvae of Pyrausta ahisUei under the 

 same conditions behaved similarly but did not advance as rapidly 

 when swimming. 



FEEDING HABITS ON THE PODS. 



The larvae of the first generation apparently utilize the green, 

 growing pod for food as well as for pupation. After the floral parts 

 fall away, the pod normally droops (PI. I, B, h) until its flat, seed- 

 bearing face is vertical, becoming erect again when nearly mature 

 (PI. I, B, c). Until maturity the seeds remain tightly embedded in 

 their sockets, and only as the pods ripen, turn brown, and dry do 

 they become loose, ultimately to be shaken out and sink in the water 

 and mud around the plants. 



In entering the young pod the larva usually selects a point just 

 below the rim and on the underside of the pod as it hangs horizon- 

 tally (PI. II, A) ; less often it cuts in between the seeds on the flat 

 face of the j)od (PI. II, C). As the larva feeds within, soft brown 

 frass is pushed out of the entrance hole in considerable quantity, 

 eventually drying and falling away or being washed off by rain. 

 The interior of the fruit or pod is filled with parench5miatous tissue 

 through which run the vascular bundles nourishing the developing 

 seeds. After entering, the larva eats out more or less of a cavity in 

 this soft tissue and often cuts into or through two or three or more 

 of the seeds. Whenever a seed is injured even slightly or the 

 vascular bundle beneath it is cut, it turns brown and soon shrivels 

 to a mere remnant. These empty or partially empty sockets (PL 

 II, B) are very conspicuous and almost invariably indicate the pres- 

 ence or work of the larvae. Such injured pods are also frequently 

 much distorted (PI. I, B, d) and very unlike the ornamental, perfect 

 specimens. Although in a few cases the cocoon was found near the 

 face of the pod and, in fact, lying partially in and through some of 

 the injured seeds, the larva usually makes its way well toward the 

 base of the pod before cocooning. 



In the pods collected at Kimberlin Heights July 19 the normal 

 number of seeds per pod varied from 10 to 25, with an average of 

 17. The work of the larvae resulted in the destruction of 5.9 seeds 

 on the average in each infested pod, or 34.7 per cent of the total 

 number in the infested pods and 5.88 per cent of those in the entire 

 jjlantation. The pods developing from the scattering flowers which 



