92 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



^j 



}hcle composed of joined ridges . . (C. S. 1560, 1574) 



5. Incomplete circle of distinct hooks . (C. S. 1674) 

 Incomplete circle of roughness without 6 



hooks. 



6. Tenth abdominal (anal) segment with (C. S. 1561, 1580) 



stout spines on ventral surface in 

 addition io two pairs of spines on 

 dorsal surface. 

 Tenth abdominal (anal) segment with- (C. S. 1607, 1635) 

 out spines on ventral surface. 



Chilo simplex (C. S. 1561, 1580), Biatrcea auricilia (C 

 S. 1560, 1574), D. venosata (C. S. 1607, 1635) and the Rice 

 Chilo (C. S. 1677) have been observed to hibernate in the 

 larval stage. 



Not much is known about C. S. 1610 and C. S. 1674, two 

 species found in cane at Dacca; of the former a single speci- 

 men was also reared from a rice stem sent from the Karim- 

 ganj Subdivision in Sylhet, and a single example of the 

 latter has recently been found in rice at Pusa. Both these 

 species were found to be injuriously prevalent in sugarcane 

 at Dacca in July 1917, whilst the ordinary cane-borers 

 found in other parts of India were not found at Dacca. 

 Sugarcane in Sylhet seems to be remarkably free from 

 borers, and the Entomological Assistant in Assam reports 

 that borers give little trouble in cane in that Province. It 

 is therefore the more curious that C. S. 1610, which is 

 present in Sylhet and injurious to cane at Dacca, does not 

 damage cane in Sylhet; and similarly that C. S. 1674, which 

 was also injurious to cane at Dacca, has not yet been found 

 at all in cane at Pusa, although it occurs in rice in this 

 district. Extensive fieldwork, combined with a thorough 

 study of the different species of borers, will doubtless throw 

 more light on these and similar problems. Meanwhile it 

 may be suggested that the damage done to cane or any other 

 similar crop by any particular borer may be connected with 

 the presence or absence in the district of particular alter 

 native f oodplants, which are preferred. 



A good deal of work has been done during the year on 

 borers and other insects occurring in the several species of 



