6 BULLETIN 184, U. S, DEPARTMENT OF AGRICULTURE. 



observed to the last three when there was sufficient huisache in close 

 proximity to the emerging beetles. In fact, the greatest amount of 

 damage to " huajilla " and " ratama " was noticed when collections 

 of huisache branches containing larvae were left near ratama and 

 huajilla trees. 



LIFE HISTORY. 



The beetles begin to appear early in September and continue to 

 emerge from their pupal cavities until the latter part of November, 

 though most of the brood issues during the month of October. In 

 the laboratory most of the material encaged developed adult beetles by 

 October 12. The adults remain for several days in their pupal cells 

 after they have emerged from the pupal cases before attempting to cut 

 their way out of the pupal cavities through the bark of the branch. 

 Just as soon as they have partaken of a little food, which consists 

 of bark from the branch, and the wing covers are sufficiently hard- 

 ened, copulation begins. Of specimens observed in the laboratory 

 none began copulating or showed activity before two days after 

 their emergence in the adult stage. This species of Oncideres, un- 

 like its near relatives, Oncideres cingulata and 0. texana^ does not 

 so frequently work in pairs. The writer has found the beetles work- 

 ing in pairs, but during midseason they occur to a greater or less 

 extent in colonies. The writer has observed as many as 24 on one 

 small tree, and two-thirds of them at times would be females. The 

 males go from one female to another, and do not seem to possess the 

 monogamous instinct. 



While making observations on the species during October, 1910, 

 it was decided to see how long a period was required for one unas- 

 sisted female to prepare the e^gg cavity and deposit an egg. The first 

 one tried deposited in 1 minute and 35 seconds, another in 4 minutes 

 and 50 seconds, and the next in 4 minutes and 40 seconds. Observa- 

 tions made later show that from 1 to 5 minutes is ordinarily required 

 for the female beetle to deposit. This, however, does not include pre- 

 paring the cavity to receive the Q,gg^ for it generally requires about 10 

 minutes to prepare the cavity. The beetle begins this cavity by insert- 

 ing both mandibles as deeply as possible into the bark of the branch 

 that is to be girdled. After forcing the mandibles deep into the 

 bark the beetle draws them together as nearly as she can. Then one 

 is removed and the other worked deeply into the puncture. It is 

 then removed and the other mandible is inserted in the same manner. 

 Later both mandibles are inserted and a tiny chip removed. Then 

 the work begins again with one mandible at a time, until the 

 cavity is prepared to receive the egg. The beetle then reverses its 

 position and forces the ovipositor into the cavity as deeply as pos- 

 sible. Shortly the egg can be seen leaving the body of the beetle. 

 After the egg is inserted the beetle frees herself by withdrawing the 



