270 THE MONTHLY BULLETIN. 



hisca per tree. Yet many growers seem to be of the opinion that by 

 introducing additional Corny s fusca into their orchard they can control 

 the scale. Mathematics as applied to insects seems rather out of place, 

 but I can make my point clear only by the use of figures. As an 

 example, we will suppose that we have a fair sized prune tree. For con- 

 venience we will divide the twigs on this tree into six-inch lengths. An 

 average sized tree would probably have about 2,000 of such twigs. We 

 will suppose that each twig bears 25 scale insects, which is perhaps a 

 fair average for bad infestations. Also suppose that the parasitism m 

 the orchard by Comys fusca is 15 per cent, a low estimate. We would 

 have then in this orchard about 7.500 Comys fusca per tree, or 675.000 

 per acre. It would obviously be of no avail to place even a hundred 

 thousand additional Comys fnsc<i in this orchard. It would be much 

 more effective and cheaper as well to spray the orchard than to attempt 

 to obtain and place therein a number of parasites sufficient to make their 

 presence felt. As the parasites far introduction can be obtained only 

 by cutting tAvigs from infested trees, the difficulty in the way of 

 obtaining the Comys fxisca, even if such a practice were effective, is 

 apparent. 



The practice of the State Insectary in the matter of distributing the 

 Vedalia perhaps should also be explained. With our present equipment 

 it is impossible for us to breed any large numbers of these beetles, but 

 a few are always kept on hand and these are sent out in response to 

 reciuests, generally in small colonies. There are still a few restricted 

 and isolated localities in the State where the Cottony Cushion scale 

 occurs and Vedalia is not present. It may have been introduced in 

 these places, and died out. or it may never have been introduced. As 

 the applications for Vedalia are many it is impossible for the Ins^ectary 

 to make the examination necessary to find out whether or not Vedalia 

 is present. Generally the person making the application is not suffi- 

 ciently well informecl regarding insects to make the examination him- 

 self. Many are familiar with the adult Vedalia but do not recognize 

 the eggs or larvae. It is therefore much easier and cheaper to send the 

 colony than to ascertain whether or not they are really needed. This 

 explanation is made for the reason that sometimes clients report a 

 wonderful "clean-up" of the scale within too short a time after libera- 

 tion of a colony of Vedalia from the Insectary. These are the cases 

 where the Vedalia was present before the new lot was liberated, but 

 their presence was not recognized. Instances of this kind have brought 

 about a popular misconception regarding the rapidity with which 

 Vedalia works. Since it is impractical to explain this matter to every 

 applicant for A-^edalia, it is only fair to state here that in most cases 

 where the scale is cleaned up this is due to the work of the Vedalia 

 already present, rather than to the small colony introduced. — H. S. S. 



The Forty-sixth California State Fruit Growers' Convention. — No 



fruit grower should forget the Forty-sixth California State Fruit 

 Growers' Convention which is to convene at Stanford University the 

 last week of July; indeed, all slioiild plan now. at once, to be present at 

 this convention, which meets the week before the meeting in San Fran- 

 cisco of the American Association for the Advancement of Science, so 

 we shall have with us some of the greatest scientists of the country. 



