ARRANGEMENT OF THE SALIVARY GLANDS 



337 



Md 



squeezed out in order either to mix with the fluid where the 2d maxillae fuse, 

 passing up into the canal in the proboscis, or to penetrate into and thus dilute 

 the semi-fluid or solid substances taken into the proboscis." 



The morphology and general relations of the salivary glands have been sketched 

 out by Hatschek, Patten, and by Lucas, from observations on those of the case- 

 worms or larval Trichoptera. 



Patten states that the spinning-glands in Neophylax are formed by a pair of 

 ectodermal invaginations on the ventral side of the embryo, between the base 

 of the 2d maxillae and the nervous cord. They 

 increase rapidly in length, and "they also unite 

 to form a common duct, which opens at the end 

 of the upper lip." 



The salivary glands in the same insect are 

 "formed by invagination of the ectoderm on the 

 inner sides of the mandibles, in the same man- 

 ner as are the spinning glands." 



Lucas has shown that in trichopterous larvae 

 (Anabolia) there are three pairs of salivary 

 glands in the head, which are serially arranged. 

 The first pair belong to the mandibular, the 

 second pair to the 1st maxillary, and the third 

 pair, or spinning glands, to the 2d maxillary 

 segment. The first or mandibular glands open 

 into the mouth at the base of the mandibles 

 directly behind the dorsal condyle. The second 

 pair open between the 1st and 2d maxillae at the 

 base of the latter, near the ventral condyle of 

 the mandibles. The third pair open into the 

 hypopharynx, which is modified to form the 

 spinneret. Lucas agrees with Korschelt in 

 regarding them as modified coxal glands, Schie- 

 menz having previously regarded the head- 

 glands of the imago of the bee as belonging to 



the segments bearing the three pairs of buccal pio _ 33n _ Ei?ht pairs of gland . 

 appendages, so that each segment originally O f Andrena: I, thoracic; II, post- 



VI, fiiterhotnandibular ; VII, sub- 

 linjrual ; VIII, liiifrual ; Mil, mandi- 

 ble ; Z, tongue ; o, eye ; ae, oesopha- 

 gus ; J, honey-sac. After Bordas. 



contained a pair of glands. It is thus proven 

 that the silk-glands are modified salivary glands 

 adapted to the needs of spinning larvae, and 

 indeed in the imago the sericteries revert to their 

 primitive shape and use as salivary glands. 



The serial arrangement of the salivary glands in the Hymenoptera, where the 

 number varies from five to ten pairs, is clearly proved by Bordas. He has 

 detected five more pairs than were previously known, and names the whole series 

 as follows: 1, the thoracic salivary glands, which are larger than the others, 

 and nine other pairs, which are all contained in the head as follows : 2, post- 

 cerebral ; 3, supracerebral ; 4, lateropharyngeal ; 5, mandibular; 6, interno- 

 mandibular, situated on the inner side of the base of mandible ; 7, sublingual ; 

 8, lingual (these and 1 to 7 common to all Hymenoptera) ; 9, paraglossal (in 

 Vespidse); 10, maxillary (very distinct in most wasps). These glands do not 

 all occur in the same species, being more or less atrophied. 



Bordas further shows the segmental arrangement of the cephalic glands by 

 stating that the supracerebral glands correspond to the antennal segment, the 

 sublingual glands to the labial, the mandibular glands (external and internal) 

 z 



