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 
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