360 



INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



THE CALIFORNIA PEAR SAWFLY 



Gymnonychua californicus Marlatt 280 (Family Nematidae) 



( Figs. 356', 357) 



Description. — The adult females are short, rather robust, shining 

 black with yellow markings on the prothorax. The antennas are black 

 and are nearly or as long as the head and prothorax, with the third 

 joint longest. The length averages about \ inch. The larva' are light 

 green, have twenty legs and are nearly \ inch long when full-grown. 



According to Matthew Cooke, the eggs are deposited under the epi- 

 dermis of the leaves and hatch in ten days. 263 



Life History.-"-— The larvse appear in April and May and begin to 

 feed upon the leaves, continuing to eat holes in the surface or on the 



m argins until full- 

 grown, which requires 

 about twenty-four days. 

 They then 'fall to the 

 ground and construct 

 small brown cocoons in 

 the soil around- the base 

 of the trees, where they 

 hibernate. The adults 

 emerge the following 

 March. There appears 

 to be but a single brood 

 a year. 



Nature of Work. — 

 The work of the larva 1 is 

 very characteristic and 

 consists in eating nearly 

 circular holes in the 

 leaves and along the 

 margins; the larvae in so 

 doing assume the atti- 

 tude as shown in Fig. 

 356. Considerable dam- 

 age is done to the foliage 

 in a few sections. 



Distribution. — The 

 California pear sawfly does not have as wide a distribution as does 

 the pear slug, but it is nevertheless quite common throughout the 

 central and northern parts of the State, having been taken in tlie Santa 

 Clara Valley, the San Francisco Bay region and the Sacramento 

 Valley. It was first reported as the pear-leaf caterpillar (Ncmatus sp.) 

 by Matthew Cooke as early as 1881-82, who observed it in the Sacra- 

 mento Valley. 201 



Food Plant. — The pear is the only recorded food plant. 



-""Marlatt, C. L., Tech. Ser. No. 3, Bur. Ent. U. S. Dept. Agrlc, pp. 122-123, L896. 

 Inj. In.s. of Orchard, Vineyard, etc., pp. 120-121, 1S81-1883. 



2fl2 The writer is indebted to W. M. Davidson for looking over this description. Mr. 

 Davidson has made careful observations on this insect for several years and is 

 undoubtedly more familiar with its life habits than any one else 



Fig. 356. — The California pear sawfly, Gymnonychus 

 californicus Marlatt. Larva? and their work on a pear 

 leaf. Natural size. (Original) 



