122 FORM OF THE PECTEN IN CERTAIN BEES. [Mar. 25, 
Is it possible that these tubes, which, as I have observed, are re- 
markably similar in appearance to those in the spider’s spinneret, 
may be of the nature of salivary glands? It is easy to imagine the 
use of such a provision in the management of the materials of the 
nests and the storing of food, even if not also in the assistance of 
digestion; while it appears to me that there is analogy in favour of 
such a supposition, the House-fly exuding from its mouth a drop of 
moisture while feeding on sugar or other hard substance, while the 
Gnat, with still another form of mouth, is supposed to inject a 
poison into the wound inflicted by its proboscis. 
I believe that somewhat similar tubes exist in the mandibles of 
some of the Bees and Wasps. 
The mandibles of some of the Apide have a transverse ridge of 
strong hooked hairs (besides other hairs in various parts). In the 
mandible of Apis mellifica 3, they are very visible. 
With the above objects I send specimens of the hind wings of 
various Hymenopterous Insects, the observation of which has con- 
firmed me in my former opinion as to their usefulness as distinctions ; 
but as I have arrived at no new results, not having had the means 
as yet of representing more than a very limited number of genera, I 
will only remark on one variation from the usual arrangement of the 
distal hooks, which occurs in the genera Sphecodes and Halictus. 
The distal hooks of the Bees are usually at regular or at regularly 
diminishing intervals; but in these two genera, one or two of those 
various parts of insects, with the exception of those which he figures Tab. 18. R. a, 
and which I have mentioned above as tubes “ in a cluster close above the maxil- 
lary palpus.”’ 
