THE AUSTRALIAN NATURALIST. 157 
reading. of papers or delivery of lectures by the more advanced 
students. It is, of course, desirable that the latter should 
assist in this direction, but not, as in the past, that it should 
be left wholly to them. Plenty of our younger members 
possess the necessary ability, all that is lacking is the equally 
necessary effort—and here is an opportunity for them to break 
the ice. 
F'p1ns.—Few people have any idea how numerous the Diptera 
is in point of species, or of its vast importance from both an 
economic and hygienic standpoint. Not only does the order 
include agricultural pests of the first importance, such as the 
Hessian fly, the fruit fly, and household pests, such as the 
house fly, but it also includes those insects which are directly 
dangerous to human life as carriers of disease, such as the mos- 
quito, the tse-tse fly, and others. The number of species of 
flies already known to science is about 40,000, and it is estim- 
ated that when all the existing species become known, the 
number will reach a total of about 350,000! In the case of 
certain species of this order, the number of individuals in exis- 
tence at any one time is enormous. Hspecially is this true 
wherever flies find favourable breeding places and plenty of 
food for their larve. Instances in point are the housefly and 
ferment flies, the latter being attracted to all kinds of decaying 
fruit, and to these may be added mosquitoes, which in gome 
districts exist in vast hordes. The Journal @ Agriculture Pratique 
says it has been found that flies have a great objection to the 
colour blue, and if tenements infested with flies are washed 
with a blue, instead of a white wash, flies will desert the place. 
In support of this, an instance is reported by that journal: “A 
farmer had 170 cows, housed in different sheds ; they were 
pestered with flies, but he observed that in one shed, the walls 
of which were a blue tint, the cows were not worried. He 
therefore added a blue colour to the lime with whith he washed 
the walls of his buildings, and from that time the flies have 
deserted his buildings.” 
Oan Puants Sun P—Can plants see as well as think? The 
opinion of the president of the British Association for the Ad- 
vancement of Science, Mr. Francis Darwin—that plants can 
remember and can develop habits, has been corroborated by 
Professor Wager, who proved to the scientists that plants not 
only can see, but can see well. He showed that the outer 
skins of many leaves are in fact lenses, very much like the 
eyes of many insects, and quite as capable of forming clear 
images of surrounding objects, This is the case with most 
leaves, but especially with those that growin the shade. These 
lenses are so good, and focus the light that falls on them so 
carefully, that photographs can be taken by means of them. 
