REPORT ON PARASITES AND PREDACEOUS INSECTS. 11 



A large number of predaceous insects were found preying upon the 

 red scale in Australia. Of the most numerous were Orcus chalybeus, 

 Orcus australasia, and Rhizobius satellus. Aside from these, numerous 

 other species of Rhizobiids were found preying upon this scale, and many 

 species of Scymnids, all of which were sent here. In my report all of 

 these are treated separately. 



On my visit to Los Angeles and Santa Barbara in the beginning of 

 September, Orcus chalybeus were found at Los Angeles, where this species 

 was liberated upon the red scale, in such numbers that we can reason- 

 ably hope they will have increased by next April, so that we may dis- 

 tribute them throughout many orchards. 



The condition in which the insects liberated by you upon the olive 

 scale were found was even better than I had expected. The species 

 present were Orcus chalybeus, 0. australasia, Rhizobius ventralis, and R. 

 debilis. Without doubt other species sent to and liberated by you will 

 appear in large numbers next spring. It is impossible to find, within a 

 couple of hours' search, all the species present in a large orchard. Orcus 

 australasia and Rhizobius debilis are feeding upon the pernicious scale 

 (Aspidiotus perniciosus) at Alameda, where they were liberated by Mr. 

 Craw, who at the same time left a number of 0. chalybeus upon these 

 coccids; but these have all disappeared, though, positively, not to die. 

 They will be found upon Lecanium or Chionaspis in time. I have never 

 found this insect feeding upon Lecanium in Australia, and did not 

 expect it would feed upon L. olese with you; but this will only show 

 that a coccid-feeding ladybird, if at liberty, will most always find its 

 food for future generations, and no doubt most of the species liberated 

 here will be found again in numbers upon some scale. 



In regard to the two species of Orcus we now possess, they were found, 

 if my observations in the field are correct, to be two-brooded in Australia, 

 the mature insects hibernating during winter. The Rhizobius are much 

 faster in breeding, and I estimate about six broods per year. The larvse 

 of these, although not numerous at the time, were found in midwinter. 



These insects here, with but few enemies, should increase about fifty- 

 fold with each brood, and from one female of Orcus we should expect 

 about 2,500 beetles at the end of the season, under favorable circum- 

 stances; while of Rhizobius, with six broods, upward of 15,000,000,000 

 beetles could be expected, and these figures will not be much out of the 

 way in your orchard, where there is an unlimited supply of food. 



On a day when the temperature reached above 100° F. in the shade 

 in Australia, the number of Orcus chalybeus upon each orange tree could 

 be estimated, as all the beetles came down on the stems near the ground, 

 which was a beautiful sight for an enthusiastic bug-hunter, and from 

 175 to 300 beetles were collected on each stem; but the larvae of the same 

 upon the trees were probably ten times as many. It should be under- 

 stood that these trees are never sprayed. 



Some 1,500 different beneficial ladybirds are known at present in the 

 world, and more than half of these will feed upon scale insects. We 

 should do our best to import as many of these as possible, and at the 

 same time guard against any new importations of coccids. 



It is not that we should exterminate our scale insects — this is a mat- 

 ter of impossibility even with the best of natural enemies or parasites, 

 and would be contrary to nature; but we can, with the proper natural 



