274 



INSECTS INJURIOUS TO THE HOP-PLANT 



length of about half an inch, or slightly less, it leaves the tip, drops 

 to the ground, and entering the stem at the surface of the vine, 

 feeds upward, 'nterrupting the growth of the vine and lessening its 

 vitality; the larva now changes color, and becomes a dirty-white, 

 with a strong, deep reddish tint, with numerous black spots. The 

 larva, now about an inch in length, and still slender, burrows down- 

 ward to the base of the vine at its juncture with the old stock, and 

 eating its way out, completes its growth as a subterranean worker; 



FIG. 201. Hop-plant borer (Hydroecia immanis Grt.): a, enlarged segment of 

 larva; 6, larva; c, pupa; d, adult, natural size. (After Howard, U. S. 

 Dept. Agr.) 



it is in this state that it is best and most widely known as the hop 

 ' grub/ and the ravages caused by it are most noted."* 



The larvae have mostly left the stems by the last of June 

 and henceforth are mainly sap-feeders. Eating into the stem 

 just below the surface of the ground and just above the old root, 

 they rapidly grow fat upon the juices of the plant. These openings 

 are gradually enlarged so that very often the stem is entirely 

 severed from the root or is so slightly attached that the plant 

 is badly stunted and yields fe'w, if any, hops. The larvae become 

 full grown from the middle to the 20th of July and are then 



* " Hop-insects," Dr. J. B. Smith, Bulletin No. 4, o. s., Division of Ento- 

 mology, U. S. Dept. Agr. 



