116 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



Cameraria agrifoliella Braun works in the upper surface of 

 leaves of coast live oak. C. alnicolella Wlsm. works in the upper 

 surface of alder leaves. C. umbellulariae Wlsm. makes blister 

 blotches on leaves of California laurel. 



The aspen leaf miner Phyllocnistis populiella Chamb. (fig. 51) 

 leaves a labyrinthian trail of frass as characteristic of its work in 

 the under side of aspen and poplar leaves. 



Common leaf miners in live oak include Bucculatrix albertiella 

 Busck and Abebaea subsylvella Wlsm. 



SAWFLIES 



Sawflies form another important group of leaf -eating insects 

 that in many cases cause extensive defoliation and destruction of 

 timber. In the Northern States and in Canada, such species as the 

 larch sawfly, the European spruce sawfly, and the jack pine sawfly 

 have been responsible for the death of as much as 85 percent of 

 the stand over thousands of acres. In the West the native sawflies 

 occasionally develop widespread outbreaks and may cause heavy 

 defoliation over limited areas, but the total timber destruction so 

 far has not been great. 



Sawflies (fig. 52) belong to the order of wasps (Hymenoptera) 

 but in appearance are usually more like flies than wasps. They 

 have thick, cylindrical bodies with four membranous wings, 

 the hind pair somewhat smaller than the forewings. The head, 

 thorax, and base of the abdomen are nearly equal in width. They 

 range in size and color from small grayish insects not over 14 mcn 

 long to large, showy species (Cimbex) over 1 inch long. They are 

 called sawflies because of a sawlike attachment which the female 

 carries at the tip of the abdomen and uses to slit open leaves or 

 stems for the reception of her eggs. Usually only one egg is de- 

 posited in each slit, but as many as 14 or more punctures may be 

 made in a single pine needle. 



The larvae resemble hairless caterpillars except that most of 

 them have from six to eight pairs of legs on the abdominal seg- 

 ments, in addition to the usual three pairs of true legs on the 

 thoracic segments. Because of their resemblance to caterpillars 

 the larvae are sometimes called false caterpillars ; and since many 

 are wormlike and often slimy, they are called slugs or worms. 

 Most of them are typical external leaf chewers, but a few are leaf 

 miners and even gall makers. 



A characteristic feature of many sawflies is the cylindrical, 

 papery, capsulelike cocoons which the larvae frequently construct 

 for pupation. Some sawflies spin their cocoons in the soil; others 

 on the debris of the forest floor ; but still others may attach them 

 to the needles or branches of the tree. 



Sawflies, for the most part, complete their life cycle with one 

 generation a year, although in some the diapause may last for 

 several years. Many species pass the winter in the prepupal stage 

 within the cocoons, and transform to adults in the spring. In some 

 species part of the brood does not emerge from the cocoons until 

 the second spring. The adults mate, and deposit eggs in the new 



