THE MONTH I. V lU LLETIX. 153 



must be nuu'h the same as the luibits of some of its elosely rehitod 

 l>uprostid relatives. Many of these beetles seek out some protected 

 location, a crack or crevice, or crawl under some irregularly formed 

 bark into which or under which the ovipositor is inserted and the egg 

 deposited. The newly hatched larva not only tinds itself well protected 

 from ()utsid(> intluenccs in this location but also from the fact that the 

 bark covci'iiig is very thin at these points the grub readily bores its way 

 into a position under the cambium. The adult of the twig girdler doubt- 

 less possesses this same instinct. In the case of Agrilus the eggs must be 

 deposited singly for at no time has there ever been found more than one 

 grub in an infested branchlet. 



Larva — By the first of September most of the larvte have reached a 

 length of something more than a quarter of an inch. At this time their 

 ojierations do not extend down the branchlet to any great distance, 

 possibly three or four inches from the point of entrance. Already the 

 presence of the little feeding grub has made itself felt, and the leaves 

 abcn'e the points of infestation show a distinct di.scoloration, and in 

 many places will be entirely dead. Growth of tiie twig-girdhn' continues 

 throuizliout the winter, the grub showing little signs of development 

 after the latter part of February, at which time it possesses a length of 

 nine sixteenths to thri'e quarters of an inch, and is very .slender, seldom 

 I'xceeding a width of one eiglith of an inch. This mature larva (Fig. 55) 

 does not do.sely resemhle the buprcstid or "Jlat-head" type of which 

 the flat-headed apple tree borer is such a striking example, but is an 

 exceedingly delicate, soft-bodied, distinctly segmented grub, possessing 

 a somewhat Hattened head which is deeidely curved in ontline antei-i- 

 oi'il.v. 'l"he general color of tlie larva is liglit cream shading into brown 

 in the more or less highly chitini/.ed portions about the regi(ms of the 

 inandil)les and at the tip of the abdomen. 



Adult — The transformation from the pnpa lo the adult state takes 

 place near the lower euil of tlie burrow, at which point the inssect makes 

 its appearaiu'c through a small round hole. The beetle is a small 

 insect moderately elongate, seldom measuring more than five sixteenths 

 of an inch in length and with a width of about one sixteenth inch. 

 The general toloration is tpiite vai'iable. ranging from bright brassy to 

 purplish or greenish and always somewhat metallic and shining. The 

 antenna' are short and .serrate, not reaching the midiUe of the thorax. 



Control. 



^Ir. S. Xakayania of Stanford University reports a hymenopterous 

 parasite (Fig. 56) attacking the larva. Fnfortunately the material 

 from which the acconii^-mying drawing was made was destroyml before 

 a determination could be obtained. The importance of this parasite in 

 the control of Agrilus is as yet unknown, as INFr. Xakayama's record of 

 the presence of a natural enemy of the twig girdler seems to be the first 

 of its kind. 



Control measures by thoroughly pruning out of infested ]iarts was 

 undertaken by the author at Palo Alto in the fall of 1911 ami 11)12. and 

 the results obtained very conclusively prove that the trouble from the 

 twig borer can be almost entirely eliminated by the occasional cutting 

 out of the attacked twigs in individual trees, even though there is not 



