18 



CIRCULAR 2 41, U. S. DEPARTMENT OF AGRICULTURE 



MIGRATION 



Aside from the local migration which occurs in passing from field 

 to field and the selection of attractive areas, the insect shows at times 

 a distinct habit of migration at night. A number of instances are 

 known where immense numbers have collected around electric lights, 

 and this would seem to be associated with some general factor which 

 brought them, perhaps the wind, as otherwise it would be difficult 

 to account for the movement from their sheltered locations near the 

 ground. Such migrations are observed during midsummer, but, so 

 far as known, no instances of the migrations in the late fall have 

 been observed. 



CONTROL 



Available control measures 

 for this species are suggested by 

 its habit of selecting the coarser 

 kinds of grass for oviposition in 

 the fall, as it is quite possible 

 to cut or burn such grass, and 

 in this way the number of eggs 

 that survive will be greatly 

 lessened. The insect jumps very 

 readily and may be captured 

 in the hopperdozer quite suc- 

 cessfully. It might also be con- 

 trolled by spraying when it 

 occurs in fields which could be 

 run over by the apparatus. 



That the species is kept in 

 check by parasites is evidenced 

 by the fact that eggs are para- 

 sitized by one of the minute 

 forms, probably Trichogramma, 

 the species undetermined. 



The occurrence of the fungus 

 Empusa grylli may also be con- 

 sidered a distinct factor in the 

 control of this species, although 

 practicable means of extending 

 its operations can not be sug- 

 gested. Doubtless the activity of predacious species of insects and 

 spiders plays a very considerable part in keeping the numbers down, 

 and birds should be expected to take a larger proportion of these leaf 

 hoppers than of the smaller species. 



Figure 3. — The inimical leaf hopper (Delto- 

 cephalus inimicus) : a, Adult, X 9 ; b, face; 

 c, vertex and pronotum ; d, female geni- 

 talia ; e, male genitalia ; f, elytron ; g, 

 nymph. (After Osborn and Ball) 



THE INIMICAL LEAF HOPPER 



The inimical leaf hopper, Deltocephdlus inimicus Say (fig. 3), is 

 one of the most widespread and injurious species among the leaf 

 hoppers, but nevertheless it has received comparatively little notice 

 in economic literature. It was first described in 1831 by Say (25, p. 

 305), who states in connection with the description: "When in the 



