no NATURAL SCIENCE. August, 



of country are of annual occurrence. These, for the most part, do not 

 destroy, but simply char or scorch the foliage of the larger trees, pro- 

 moting a vigorous growth of young suckers shooting up from the base 

 of the trunks or roots, the tender foliage of which forms a dainty 

 lodgment for hundreds of insects, and is especially suitable for gall 

 producers. 



Before proceeding with a brief account of some of our most 

 characteristic galls, we will take a glance at their food-plants, as 

 certain groups seem to have a decided preference for allied species. 

 The Cynipidae are found upon Acacias and Eucalypts ; the galls of 

 the Psyllidae upon the Eucalypts ; the Cecidomyia (gall gnats) attack 

 Eucalyptus, Melaleuca, Leptospernmm, Omalantlius, Acacia, and Frenela ; 

 while though the greater number of our gall-making coccids confine 

 themselves to Eucalyptus, some of the smaller groups also attack 

 Casuarina, Leptospevmum, and Melaleuca. 



Both the form and the structure of the dipterous galls, all of 

 which belong to the family Cecidomyia, are very variable. One of 

 the commonest, Cecidomyia Frauenfeldi, Schurer, about the size of a 

 small filbert, is composed of a number of papery scales over- 

 lapping each other like the petals of a rosebud, while the larva lies 

 curled up at the bottom close to the point of attachment to the twig. 

 Very different are the round, hard, shot-like galls of Horotomyia 

 Omalanthi, Skuse, often covering the leaves with their rounded reddish 

 warts. The structures of Diplosis fyenela, Skuse, are very remarkable, 

 being subglobular, fruit-like galls, formed of three thin valves growing 

 upon the slender branchlets of the desert pine (Frenela Endlicheri). 



Those that infest Acacias produce curious tubular galls. 

 Cecidomyia acacics-longifolia, Skuse, aborts the young seed pods, altering 

 them into irregular masses of tubular cells, each containing a 

 larva, and occurring in such numbers that every seed pod on one of 

 these trees is thus transformed. 



Hardly anything is known about the Cynipidae belonging to this 

 country, but I have described three species (placed provisionally in 

 the genus Cynips) all of which are found upon the Acacias, though I 

 Icnow several Cynips galls upon the Eucalypts. 



Cynips acacia-longifolia attacks the flower-buds, aborting them into 

 large rounded soft masses which, when mature, are handsomely tinted 

 with red and yellow, from which they obtain the not inappropriate 

 name of *' Acacia apples " ; C. Maideni produces galls upon the 

 branchlets and twigs of the same Acacia, often altering them into 

 swollen gouty excrescences six or seven times their natural size ; 

 C. acacia -discoloris deposits its eggs in the leaf-buds, which change 

 into oval hollow galls ornamented with three short prongs or horns at 

 the apex. 



In the Homoptera, the family Psyllidae contribute a number of 

 rounded woody galls upon the leaves of the Eucalypts. In one 

 species the larvae form soft fleshy galls of a brilliant red tint, so 



