270 Annals Entomological Society of America [Vol. XV, 



forms studied but found a compound gland in the prothorax. This is 

 the condition of L. indivisus and P. inter r up ta, although the structure 

 of the two glands is not the same. In P. interrupta it resembles the glands 

 found by Gilson in P. grandis and is much branched, Plate XVIII, 

 Fig. 9, and Plate XIV, Fig. 2, ggl. The gland in L. indivisus is single 

 and lies above the prothoracic ganglion, its opening is between the 

 connectives of this ganglion to the sub-cesophageal and connects with a 

 spinneret which lies at the extreme anterior margin of the prothorax 

 and extends forward under the head, Plate XV, Fig. 1, at ggl, Plate 

 XVIII, Fig. 1, ggl, and Fig. 10. In H, analis a gland, corresponding 

 to this gland of Gilson, has not been found. 



Glands in the Head of Limnophilus indivisus Walker. 



In the head are six pairs of glands exclusive of the silk glands. 

 Lucas, 1893, Henseval, 1895, and Russ, 1907, mention two pairs and 

 term them mandibular and maxillary glands. L. indivisus possesses 

 these two pairs and others. The mandibular gland is situated on the 

 outer angle of the mandibular sclerite and is composed of a number of 

 single celled glands or " pockets" which open into a common duct. 

 This common duct leads to the base of the sclerite, the name of which 

 it bears, Plate XVIII, Fig. 14. The maxillary gland, as Lucas so terms 

 the second of the head glands, is similar to the mandibular but is com- 

 posed of many more of the small single celled glands. The two glands 

 lie underneath the oesophagus with their several small lobes folded 

 upon each other and their ducts extending almost at right angles from 

 each other. These ducts open into the buccal cavity at the inner margin 

 of the mandibular sclerite, Plate XVIII, Fig. 13. Patten, 1884, states 

 that they are an invagination of the inner margin of the mandibular 

 sclerite in the embryo and Patten terms them salivary glands. Further 

 ventrad in the lead lies a multicellular gland in the maxillary sclerite 

 with an opening into the distal end of this sclerite, Plate XVII, Fig. 12. 

 In the labium we find a pair of similar glands, Plate XVIII, Fig. 1 1 . With 

 these glands hitherto undescribed, and which we must, from their position 

 at least, term maxillary and labial glands, the so-called maxillary glands 

 of Lucas present a problem for nomenclature. Lucas ventures the 

 theory that the glands of the head are coxal glands and the homologs of 

 the parapodal glands of the annelid. If this theory be accepted then 

 the maxillary sclerites may not be possessed of two pairs of glands nor 

 may the mandibular sclerites. The writer prefers to use Patten's name 

 of salivary- gland, for the maxillary gland of Lucas. 



Glands also exist at the base of the antennas and below the visual 

 area, but these are not figured. 



Circulatory system of L. indivisus: This is simple as in all insects 

 and consists of the dorsal vessel which extends from the ninth segment 

 of the abdomen to the head, where it spreads out upon the supra- 

 cesophageal ganglia. There are nine pairs of alary muscles beginning 

 between the metathoracic and first abdominal segments and continuing 

 to lie between the segments as far back as between the eighth and ninth. 

 The first four are slender but the remaining five are heavy and connect 

 with the one in front and behind it. In front of each pair of muscles, a 

 valve exists in the dorsal vessel, Plate XIV, Fig. 8. 



