Xo. 489] 



SILK GLANDS OF A PAN TELES 



577 



The dense secretion ooverino- the inner snrface of the 1st thoracic 

 portion indicates that tliis is its own peculiar product and not that 

 of the fohovvinfr (Hvision. T]n> secretion appears closely striate 

 in a rmhal manner. Acid liaenialuni and eosin do not color it; 

 iron haeniatoxylin, safranin, and (irenacher's borax carmine stain 

 it but sli^ditly. The central colinnn of silk, however, is more 

 densely stained with iron haeniatoxylin and safranin. 



As the glands of Fhilippi are not present it is only speculation 

 to suppose that the secretion of the second thoracic portion may be 

 of a nature similar to that of these jjlands in the Lepidoptera. The 

 function of the product of the olands of Philippi is not definitely 

 known. Nearly all workers dill'er in their conclusions in regard 

 to this question. The conclusion of Blanc, 'Ul, and Berlese, '()(>, 

 based upon the experiments of Robinet, '30, seems the most logical. 

 These authors consider its finiction that of lul)ricatin<: the threaii 

 which is to pass through the i)ress. 



The fact that the thread, in Apan1rJi\^ (jlomrmitts, begins lo take 

 on its definite form at the posterior end of the 1st thoracic ])ortion 

 might indicate that the secretion of the 2nd division had a coagu- 

 lating effect upon the silk and "gres." 



SUMMARY 



1. The silk glands of Apanirirs- rjlomemlu.^ differ from those 

 in the Lepidoptera and Tric-hopt.'ra in that then- are four tubo 

 in the abdtmiinal region. TluMr histological structure is similar 

 to that of Lepidoptera and TricliojJtera but difiers markedly from 

 that described for the tentliredinid larvae. 



2. In immature larvae the epithelial cells of the whole produc- 

 ing region are actively secreting. Ximierous ^■acuoles are present 

 in these secreting cells, especially near the periphery. 



^ T,i nlon.I-; (Iv.-,! in Fl , M 1 M .1 i 1 1 < .'s solutiou aud staiucd with iron 



