A STUDY OF THE FACTOES OF CONTROL. 91 



many times greater in extent than the comparatively narrow enltivated 

 l)elts, this method of coping with the problem appears to be hopeless. 

 In fact, if all the beetles were captured and paid for at the ruling rate 

 -of Is. to 2s. a ciuart, there would not be money enough in the State 

 Treasury to settle the bill. Undoubtedly some "relief comes from this 

 ])ractice, especially where the beetles are collected persistently for 

 years ; but a review of the figures and history of collecting in the worst- 

 infested districts gradually led me to the conclusion that the expense 

 Avas too great when compared with the results. Furthermore, other 

 factors were probably largely responsible for the remarkable disappear- 

 ance of the pest in certain districts, especially those which suddenly 

 become immune. 



The celebrated economic entomologist Mr. Albert Koebele (1) first 

 recommended hand-collcting of these terrible cane-pests in Australia, 

 and the Colonial Sugar Refining Company (10) (35) (36) have 

 persistently worked on this advice at their Queensland mills. i\Ir. Tryon 

 (19) (46), too, has repeatedly urged this procedure. With deference 

 to the opinions of these experts, let me say that the difficulties of 

 collecting beetles while they are on the feeding-trees have greatly 

 increased in recent years. Lantana in mRuy places occupies the ground 

 to such an extent under the trees that it is almost impossible to secure 

 the beetles once they are shaken off. 



We have demonstrated recently, however, that all the beetles flying 

 to the cane in the morning are gravid females ready to oviposit. By 

 dissecting I found that these had an average of 26 eggs each. After the 

 morning flight ends at 5.30 a.m., the beetles have a rest for a considerable 

 period, hanging upon the cane-leaves. Hence, between the time the 

 flight ends and about 7 a.m., it will probably prove practicable to collect 

 these females daily, during the whole of the aerial life of the beetles. 

 AVhere the cane is 2iot too high, it is possible to see the conspicuous grey 

 beetles on several rows at a time, as one walks through the field, so that 

 it is not difficult to collect a good lot each morning. This procedure 

 would certainly be far easier and more profitable than picking up the 

 grubs later in the season after they have become injurious; for every 

 beetle picked from the cane-leaves at that time saves 26 grubs from 

 hatching. 



On the other hand, it Avill be remembered that at times during the 

 flight a considerable majority of the beetles in the feeding-trees are 

 males — I have found as high as 86 per cent. — so it is a waste of funds 

 to pay for the collection of these. 



Air. Koebele (1) suggested the use of light-traps for the destruction 

 of cane-beetles. The Colonial Sugar Eefining Company (10) gave 

 considerable attention to the trapping of beetles at Hambledon in the 

 early days. Casks were placed in and around fields; each cask was 

 partly filled with water, a tallow lamp was made fast to a board nailed 

 across the top, and tar or molasses was smeared all over the outside of 

 the cask. It was reported that thousands of beetles were caught in this 

 manner. 



Beetle collectors have told me that it is a well-known habit of the 

 greybacks to fly to lights, especially when a lamp is placed under the 

 feeding-trees in the middle of a white sheet. Mr. Jarvis (68) experi- 

 mented somewhat on this phase of the control, and constructed an 

 elaborate trap, the design of which was published (81) later. Yet 



