579 



of which the surface is at all moist. The only successful attempts 

 in colonisation have been where sugar-beets were sub-irrigated and 

 several inches of dry soil kept at the surface. It therefore seems 

 highly impoii^ant that sugar-beet fields should not be allowed to become 

 dry during the period when P. helae is migrating to them. This is 

 frequently just the time when, in ordinary practice, these fields are 

 allowed to become quite dry. Instances on record show that, 

 irrespective of Aphids, early and frequent irrigation is the right treat- 

 ment for obtaining the highest sugar content and tonnage. Plenty 

 of moisture should be maintained throughout the growing season, as 

 this will prevent the increase of such individuals as have succeeded in 

 becoming estabHshed in the fields, even if well irrigated. 



Craighead (F. C). Larvae of the Prioninae. — U.S. Dept. Agric, 

 Washington, D.C., Report no. 107, 25th June 1915, 24 pp., 



8 plates. 



Cerambycid larvae are probably without exception phytophagous, 

 mainly boring in the ligneous tissue of trees, although a few species 

 are confined to herbaceous plants, in which case they are usually pith 

 or root feeders. Some species have a wide variety of host plants, 

 while others are limited to a single genus or species. Great diversity 

 is shown in feeding habits and larval mines ; some bore exclusively 

 in decayed moist wood, others in dead, dry wood, and many under the 

 bark of living trees. The manner of oviposition also varies. Many forms 

 lay their eggs in crevices of the bark ; others insert them into the soft 

 wood ; in some cases, e.g., Parandm, it is probable that the adults 

 do not emerge, but pair and oviposit in the wood in which they are 

 working. The life-cycle usually lasts for a year, although in some cases 

 from two to three years is the normal period. A detailed description 

 of the genera of the sub-family Prioninae is given. The larva of 

 Parandra is t\qDically a heartwood feeder, attacldng nearly all eastern 

 coniferous and hardwood trees. It normally attacks the lower trunk, 

 gaining entrance through a wound. This species has been recorded 

 as a serious pest of park and shade trees, as well as of telegraph and 

 telephone poles. Mallodon dasi/stomiis, Say, has been taken from 

 willow, oak and box. Archodontes {M.) melanopus, L., bores into 

 the living roots of oak, causing the formation of a large gall and often 

 killing the trees or giving rise to a stunted growth. The larva of 

 Orthosoma is found in dead and decaying logs of practically all arbore- 

 scent species of eastern hardwoods and conifers. It is chiefly of 

 economic importance owing to the destruction it causes to teVgraph 

 and telephone poles and other timbers in contact with the groimd. 

 Ergates spiculatus, Lee, attacks dead or decaying coniferous logs. 

 The mines are very large, extending through both sapwood and heart- 

 wood. The principal flight of the adult is in July and August. 

 Prionus imbricornis, L., occurs throughout the eastern and central 

 States on the living roots of oak and chestnut. The adults fly from 

 June to August. In West Virginia it is especially destructive to 

 chestnuts, causing the death of the tops and branches. The females 

 lay eggs in groups about the base of the tree. The young larvae feed 

 in the bark before penetrating into the heartwood of the root. The 

 larval stage extends over at least three years. P. laticollis, Drury, 



(C208) b2 



