MR. TUFFEN WEST ON THE FOOT OF THE FLY. 403 
their tibiae. But with the Strepsiptera and Physopoda all the hooks are wanting. The 
Diptera and many Hyrnenoptera have moreover under these hooks softl obulcs {arolia) 
provided with numerous small papilla^ by means of which these insects can fix themselves 
to objects." 
To this, the editor of the American edition adds : — " The Tenthredinidue have a lobule 
of this kind on each of their legs, and the Diptera have even two to three." 
" According to Blackwall the papillae of the arolia secrete a viscid substance, which enables 
the Insecta having these organs to walk on smooth and steep surfaces. But this assertion 
requires further proof, though admitted by Spence." 
It must not be imagined that the above is a correct representation of the knowledge 
possessed in this country on these structures. Not one statement is quite correct. Thus 
1. The structure of the tarsi in the Curculionida3 was correctly described nearly two 
centuries ago; they do not grapple objects by means of the immoveable hooks on their 
tibiae, chiefly, but by their tarsi, in which action the former will of course sometimes bear 
a part, but even then only a very subordinate one. 
2. The feet of the Strepsiptera and Physopoda differ so essentially that a comparison 
instituted between them solely on the ground of the presence or absence of claws cannot 
be considered a happy one. The tarsal joints of the Btrepsipterous feet somewhat re- 
semble a series of fly's pulvffli strung together; a dense brush of bans covers the under- 
surface of the joints. The legs of the Physopoda are terminated by minute, naked 
bladders. 
3. The comparison between the feet of Diptera and of Hyrnenoptera is equally unfor- 
tunate. The structure of the former had been, as I have shown, repeatedly described with 
a near approach to accuracy, even before Blackwall's observations; the latter was, I 
believe, correctly described for the first time by myself. The observations will be given 
future communication 
4. The TenthredinicUe are Hyrnenoptera, with the type of foot of their Order, and with 
in addition, small cushions underneath each tarsal joint; which peculiarity, though it ai 
once attracts the attention of any one who looks carefully at the feet of an example of thn 
genus, is not mentioned by the editor of the work in question. 
About the same time a series of brief descriptions of the microscopic structure of Insects 
feet was published by Dr. Inman*, who describes the feet of not less than thirty-on< 
species of Articulata, mostly of the order Insecta. Allusion will have to be made V ^~ 
These 
ks presently ; from the figures given, I judge that many of the description 
made from preparations of the parts, mounted as " objects for the microscope." 
are selected for their beauty alone ; and, from the way in which they are prepared, it not 
unfrequently happens that they tend to convey ideas of structure and relations of a very 
erroneous nature. I gladly bear my testimony to the real merits of this paper, and to 
the benefit I have derived from the suggestive nature of many of the remarks in it ; at 
the same time an expression of regret cannot be withheld, that 
the illustrations 
unworthy of the remarks to which they are appended 
* <• 
Liverpool 
Scientific Society, No. 6, 1 85 1 . 
XXIII 
3 
