70 MISC. PUBLICATION 273. U.S. DEPT. OF AGRICULTURE 



legless, and without a distinct head. Over 200 species are described 

 from various plants in the Western States, but only a few do 

 appreciable damage. 



GALL MIDGES 



The gall midges belonging to the family Itonididae are re- 

 sponsible for the formation of a great variety of small galls on 

 many different forest trees and plants. The adults are tiny pink 

 flies resembling mosquitoes and are called midges. The larvae are 

 small pink or red maggots, without legs or definite head, but with 

 a dark "breastbone." Almost any part of the tree may be affected, 

 but most galls are formed on the needles or leaves, in the cones or 

 seeds, or in the bark of twigs. A few species on forest trees are of 

 some economic importance. 



The Monterey pine midge (Thecodiplosis pini-radiatae S. & M.) 

 works at the base of the newly formed needles of Monterey pine 

 and other pines in central California and causes them to become 

 swollen and shortened (fig. 29). Sometimes heavily infested twigs 

 are killed and the ornamental value of the trees is seriously im- 

 paired. Other species that produce swellings at the base of needles 

 on pines include Janetiella coloradensis Felt on pines in Colorado 

 and Utah, and Thecodiplosis eockerelli Felt on pinyon in Colorado. 



Apical budlike swellings are formed on ponderosa pines in Colo- 

 rado bv Contarinia coloradensis Felt and Dicrodiplosis gillettei 

 Felt. 



Several of the juniper galls are caused by species of gall midges. 

 Walshomijia juniperina Felt causes a slightly enlarged fruit or a 

 purplish, apical bud gall with three or four diverging lobes on one- 

 seed juniper, and W. insignis Felt makes an oval, apical bud gall 

 on Rocky Mountain juniper. Oligotrophus betheli Felt forms red- 

 dish, apical, conical galls on Utah juniper. Alio my ia juniperi Felt 

 produces a prickly, burrlike bud gall with numerous short, straight 

 leaves and none reflexed on Utah juniper. Rhopalomyia sabinae 

 Felt attacks juniper in Colorado and Utah and produces thick- 

 walled, purplish, apical bud galls which split open in four sections 

 when the midges emerge. 



Some of the pitch or gall midges attack the tender twigs or ter- 

 minals of young trees and, by forming pitch pockets under the 

 bark, either cause their death or the deformation of the wood. 

 Their work can be recognized by the small pink or red larvae 

 found imbedded in pitchy pockets or galls under the bark. The 

 adults are frail, two-winged flies or midges resembling mosquitoes. 

 Many of the western forms have not yet been named. 



The bird's-eye pine midge (Retinodiplosis sp. near inopsis 0. S.) 

 is a common species in southern Oregon and California, where for 

 many years it has killed the lateral tips of many young ponderosa 

 pines (fig. 30). In some years this damage has been so severe as 

 to deform and sometimes actually kill the trees. The damage is 

 first noticeable very early in the summer, when the new lateral 

 shoots fade, droop, and gradually turn yellow and die. On some 

 trees nearly every new shoot is affected (2). On examination of 



