404 THE ALIMENTARY CANAL OF THE IMAGO. 
insects examine their food with the maxillary palpi, and I have 
frequently seen the palps immersed in a drop of regurgitated 
fluid, when the proboscis is withdrawn into the head capsule. 
Near the extremity of the palpus there are always a number of 
transparent spots, which appear as perforations. I have been. 
unable to obtain a section showing these as openings in the 
cuticle; beneath each there is what appears to be a tricho- 
genic cell surrounded by nerve-cells. These perforations have 
been described as pores, and it has been supposed that they 
permit sapid fluids to come into contact with the nerve-end 
organs. 
The pharynx contains two rows of fine sete, which are 
undoubtedly connected with nerve-terminals. These are 
situated on the epipharyngeal plate, one row on either side of 
the median raphé. The extremities of these sete are directed 
backwards towards the cesophagus. 
f. The Salivary Glands. 
In the imago of many insects two very distinct forms of 
salivary glands are frequently present in the same individual, 
besides one or more pairs of small accessory glands — the 
tubular sericterial glands, lingual glands, which either form, as 
in Blatta and the larva of Musca, large thin-walled sacs, or, as 
in the imago of Musca, long convoluted tubes ; and a pair of 
racemose glands, the ducts of which join the ducts of the 
lingual glands. In Volucella and the Syrphide, and probably 
in all pollen-feeding Diptera, as well as in the Hymenoptera, 
the racemose glands are largely developed; whilst in the 
Muscide they are absent, and only the tubular sericterial glands 
are present. The latter are just as well developed in the 
Syrphidz which possess racemose glands, as in the Muscidz ; 
hence we cannot regard them as modifications of one and the 
same organ. Neither can I hold that the large sac-like glands 
in Blatta are mere salivary reservoirs, as is usually held. I 
must regard them as sericterial and homologous with the 
tubular form of gland which co-exists with the racemose glands 
in so many of the Insecta. 
