INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 351 



HYMENOPTERA (Order) 



MEMBRANOUS-WINGED INSECTS 



BEES, WASPS, GALL-FLIES, SAWFLIES, HORNTAILS, ANTS. 



This is the fourth largest order of insects, comprising not only some 

 of the most beneficial forms like the honey bees and parasitic insects. 

 but some very injurious forms like the sawflies and Argentine ant. 

 The transformations are complete, the larva being maggot or grub- 

 like and the pupa quiescent. The adults usually have four well 

 developed membranous wings and are powerful fliers, but a great 

 many members have no wings at all. The jaws are well developed 

 for biting, but the other mouth parts may be modified for sucking and 

 lapping. There is a very extraordinary phenomenon of the repression 

 of sex maturity and the development of a sting in the females of 

 certain families, while the phenomena of virgin-birth and the forma- 

 tion of galls are no less wonderful. 



SIRICOIDEA (Superfamily) 



HORNTAILS 



The horntails somewhat resemble the sawflies in general appearance, 

 coloration and the two-segmented trochanters. The ovipositor, how- 

 ever, is in the form of a long spear or horn and not saw-like, and there 

 is but one apical spur on each front tibia instead of two. The larva 1 

 usually feed within the small twigs or in solid wood. The tip of the 

 abdomen is curved backwards and ends in a small pointed tubercle 



THE WESTERN GRASS-STEM SAWFLY 



Cephus occidentalis Riley and Marlatt (Family Cephidae) 



(Fig. 348) 



Description. — The adults are shining black, spotted and banded 

 with yellow and about £ inch long. The larva? are yellowish- white with 

 head, pronotum, palpi rings, tips of paired circi and seta? of the last 

 abdominal segment, pale yellow. The mandibles are dark. They are 

 larger near the head, tapering towards the tip, which ends in a brown 

 tubercle. When fully-matured they are § inch long and one eighth as 

 wide. Though one of the horntails, this insect is commonly known as 

 a sawfly. 



Life History. — The eggs are laid singly upon Hie stems of the food 

 plants in May and June. Immediately upon hatching, the larva? bore 

 down the stems and reach the ground in the fall. Within the stem 

 near the surface of the ground they enlarge the burrow and remain 

 there, quite active during the winter. At the enlargements the stems 

 are greatly weakened and break off. Within them a silken eocoon is 

 spun and pupation takes place in the spring (April and May) and the 

 adults issue in May and June, when e"g-laying begins. There is but a 

 single brood a year. 



Nature of Work. — The stems of the infested plants become dis- 

 colored and break off at the cell made in the fall, near the surface of 

 the ground. Much damage may be done. 



