Thomson's manual of Pacific Northwest finance

Bibliographic data

Monograph

Identifikator:: 1838857176

URN:: urn:nbn:de:zbw-retromon-229226

Document type:: Monograph

Title:: Thomson's manual of Pacific Northwest finance

Place of publication:: Seattle

Publisher:: Thomson's Statistical Service

Year of publication:: 1930

Scope:: XXX, 487 Seiten

Digitisation:: 2022

Collection:: Economics Books

Usage license:: Get license information via the feedback formular.

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Section VIII. Industrials

Collection:: Economics Books

Co PART 1V. Hyperaspis delicatula, Muls. Abundant and invaluable. Scymnus guttulatus, Sicard. Nearly as useful as the last species. Scymnus sp? Also one of the commonest and most important predators. Platynaspis kollari, Muls. Scarce. Platynaspis capicola, Crotch. Locally common. Also two other un-named species, each scarce. OrpER Diptera (Two-winged Flies). FamiLy Syrphide. Syrphus adligatus, Wied. Xanthogramma calopus, Liw. Xanthogramma pfeifferi, Big. These three species are primarily aphis-feeders, but have each on occasions been found devouring mealy- bug. There are probably other species of Syrphide which may at times feed on mealy-bug. FamiLy Agromyzide. Leucopis sp.? Abundant and invaluable. As an indication of the relative abundance of some of the commoner of these predators, the following figures show the emergences from some mealy-bug attacked coffee twigs collected in March, 1926, from a plantation which was then, and had been for some time, heavily infected with mealy-bug. The amount of the infected material was such as would go into two boxes each 18 ins. x 11 ing." x 9 ins. Psocoptera, various species ... oh i 1831 Chrysopa sp. -.. hit “ a oh 3 Eublemma costimacula oe = oo Wa Chilocorus angolensis ox i be 17 Hyperaspis delicatula i pie {33 232 Scymnus guttulatus ... hi 3 ied 74 Scymnus sp? ... oe as aoe oa 282 (Total Lady-birds: 605.) Leucopis sp? _... ol C 2s 283 Total number of Predators .. 2731 It must of course be remembered that as soon as this material was collected, none of these insects were exposed to adverse weather conditions, nor to the depredations of their principal enemy the ant; nothing like the same number would have survived from the same material left to itself in the field. Why then, with such an abundance of beneficial insects in existence, is the coffee mealy-bug a pest? Some of these predatory insects have, it is true, their own particular enemies. Thus three of the lady-birds, namely Chilomenes lunata, Hyperaspis senegalensis, and Scymnus sp. are sometimes parasitised by various species of Chalcids. So also are all the four species of Diptera mentioned, and one, at least, of the Hemerobiids. But the harm done by these does not amount to much—the two most heavily parasitised, Hyperaspis and Leucopis, only seem to be attacked to the extent of some 109, at most. There are also several predatory insects which take their toll of the beneficial ones, for instance Mantids may catch an occasional lady-bird, and various fossorial wasps sometimes prey on the larve of Chilocorus. = A large 199

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