1891.] ESSAYS. 61 



almost completely infested with a dark-colored aphis, or louse, 

 upon which tobacco smoke seemed to make no impression. Tiiey 

 nearly covered the under side of the leaves and soon sucked the 

 life out of them. The whole crop was destroyed fully a month 

 before they would have ceased bearing, if nnliarmed. 



Twice, specimens of these insects were sent to the Hatch Ex- 

 periment Station, but both times failed to reach the Professor of 

 Entomology before the leaves became dried up and the insects in- 

 visible. Once the professor was at South West Harbor, Maine, 

 on a vacation, and the insects were forwarded to him from Am- 

 herst. Why the second installment should have failed to reach 

 his assistant at the station I know not. 



I afterwards sent some cucumber leaves from the later vines 

 in out-door frames, which were infested with a similar pest, if not 

 indeed identical. My son was doubtful al>out tiieir being the 

 same insects. Prof. Fernald pronounced tiiese the aphis cu- 

 cumeris, a real plant louse, l)ut the " life history of which has not 

 yet been fully made out." He says, " There appears to be three 

 forms: 1st, wingless females like those you sent; 2d, males and 

 females with wings, wiiich pair and lay eggs, but where is not 

 known ; 3d, a wingless form that feeds on the roots, dift'ering 

 considerably from those you sent." 



He mentions " Road dust, Pyrethrum ])owders, tobacco smoke, 

 and kerosene emulsion ; all which liave been tried with varying 

 success," he says. But he suggests avoiding growing cucumbers 

 on the same ground next year wliere these pests appeared last 

 season. He makes the same suggestion for squashes, melons, 

 etc., that have been similarly infested. 



For the destruction of the root-infesting aphis, he recommends 

 tiie use of " bisulphide of carbon, half a teaspoonful poured into 

 a hole two inciies or more deep made in the ground about three 

 inches from the stem of the plant. Then press the dirt together 

 and down into the hole as compactly as possible." 



" The liquid changes to a vapor which is deadly to insect life, 

 and as it permeates the soil it reaches the roots and destroys the 

 insects feeding on them. It must not be used where there is a 

 light, as an explosion might occur." 



Cucumbers grown in out-door hot-bed frames or following let- 

 7 



