A Study of some of the Common Trees in their 

 relation to the Aerial Life of the Beetles. 



By Alan P. Dodd. 



A botanical survey of the area surrounding canefields with regard 

 to the aerial life of Lcpidodenna alhohirtnm is both interesting' and 

 instructive. Two features are outstanding and at once impress themselves 

 on the mind : firstly the number and variety of the trees used for food 

 by these beetles, and secondly the frequent close relationships between 

 food plants and those innnune from attack. Try on (19) was the first to 

 make the former observation; the list of feeding-trees given by him 

 contained twelve species, representing four families ; he thought that only 

 scrub trees were attacked. Girault and Dodd (66) included about twenty 

 trees in their list, compiled from direct observation, and, moreover, 

 ■expressed their belief in the imnumity of certain trees from assault by 

 the beetles; and as they summarised existing data briefly and suitably 

 we cannot do better than cjuote from their Ijulletin : — 



''Trees on the edges of canefields are usually chosen for feeding 

 purposes but all through the forest and often a mile or two from 

 canefields beetles can be found. . . . Sometimes hundreds of beetles 

 will congregate on one tree to feed, es]>ecially if the tree be large, but 

 as a general rule only a small number collects on one tree. Special 

 situations are often chosen, and numbers may be gathered day after day 

 in one small area, where none can be found elsewhere in the neighbour- 

 hood. Trees of any size may be selected, but small shrubs and saplings 

 (from 8 to 25 feet high) appear to be preferred; however, a large tree 

 will often attract scores of beetles, while rarely is a small one crowded. 

 That certain food plants are favoured is evident ; observations, however, 

 have been restricted to seasons when the beetles were comparativel}" few, 

 and in abundant seasons trees may be attacked indiscriminately. Food 

 plants may belong to almost any order, whereas trees in the same genus, 

 and obviously closely related, may or may not suffer defoliation. Jungle 

 {i.e. scrub) or forest trees are attacked without ditference. Around 

 Gordonvale the country is mostly forest, which may account for the 

 preponderance of forest trees given in the food list. Tryon (1896, p. 19) 

 remarks as follows: — 'Since their {i.e. the beetles') food is yielded almost 

 wholly by the leaves of so-called scrub trees, they are almost exclusively 

 founci within or in the vicinity of scrubs, or along the course of creeks 

 that are fringed by scrub vegetation.' Our experience at Gordonvale 

 shows that the beetles feed throughout the forest land as well as on the 

 fringes of jungle vegetation. This may be accounted for l\v the prevalence 

 of forest {i.e., open bush with typical Australian EiicalijpfKs and other 

 flora) lands." 



The great majority of our observations has been made around 

 'Gordonvale, w^here open forest country predominates ; scrub only occurs 

 in isolated patches, or in fringes along streams or gullies. We have paid 

 spasmodic visits to other districts, noting feeding-trees there; but no 

 comprehensive study of this phase of the subject has been undertaken 

 outside the locality stated. Hence, probably many food plants have 

 been overlooked, especially in scrub districts. 



