190 • [January, 



the dorsal side, but both Prof. Comstock (p. 282) and Dr. Emanuel 

 Witlaczil (p. 160) refer to them as situated on the ventral side. The 

 latter author very decisively states this to be the case. My own ob- 

 servations confirm this opinion, although I suppose it is not intended 

 to maintain that in life they really open on to the external ventral 

 superficies, but only towards the ventral side, being really situated, as 

 I think, within the insect, and which I suppose prevents them being 

 seen until the insect has been treated with a re-agent. Targioni- 

 Tozzetti and Signoret appear to have been the first to describe these 

 organs as spinnerets, the latter author's term being " filieres agglo- 

 merees," and Dr. Witlaczil seems also to suppose that they secrete 

 the scale-making material, for he says (p. 160), " Nach dem Ausein- 

 andergesetzten ist es wohl ziemlich sicher, das wir es hier auch mit 

 einer Art von Wachsdriisen zu thun haben, wen auch ihre Aufgabe 

 nicht aufgeklart ist." Prof. Comstock describes them as " spinnerets," 

 and finally Mr. Maskell, in his "Account of JSTew Zealand scale-insects/' 

 adopts the same designation. 



It isfonly after prolonged consideration, that I now venture to 

 offer a suggestion as to the functions of these glands, which is at 

 variance with the opinions of the distinguished authors whom I have 

 mentioned. It appears to me that these glands are not used for the 

 purpose ofJsecreting the scale substance, but that they are analogous 

 to what Burmeister (Man. of Ent. Shuck. transl.,pl. xxii,figs. 6 and 7) 

 terms "ventral salivary glands," and I think that they are intestinal 

 glands with digestive functions analogous to what in animals are 

 termed the glands or crypts of Lieberkuhn. I will now endeavour, 

 as far as^I am able, to establish the reasons for arriving at that con- 

 clusion. I may mention first that Comstock (p. 282) significantly 

 mentions in a foot note referring to these ventral grouped glands, that 

 he has observed " similar compound spinnerets near the base of the 

 oral seta? in several species." I think it may reasonably be concluded 

 that these organs near the base of the oral setae were the submaxillary 

 salivary glands, which have been well described and figured by Dr. 

 Mark in his " Beitrage z. Anat. und Hist. d. Pflanzenlause insbesond. 

 d. Cocciden." The similarity, therefore, of these salivary glands- with 

 the ventral grouped glands as mentioned by Comstock is suggestive.- 



If, on the other hand, these ventral glands were used for secreting 

 scale-substance, it appears to me that they would open on the dorsal 

 superficies of the insect, because the insect lies underneath its 'scale, 

 and also one might expect that all the species which spin scales would 

 be provided with these organs. But this is not thecase ; for instance 



