692 Pomona College Journal of Entomology 



When the spiracles are retracted, the tracheal tube between the sac and ca)iut 

 shortens (it seems to be very elastic), drawing the evaginated portion after it 

 into the invaginated pocket. These stigmata, also, are covered with a thin sieve- 

 like, ciliate membrane. 



The other metiiod used in the internal study was imbedding in paraffine and 

 sectioning serially with the microtome. Two killing reagents were tried. Hot 

 water at about 9^ degrees Centigrade was found to be very effective in both killing 

 them quickly, and, also, distending tlie body and preventing its contraction. After 

 being in the liot water for a few seconds the larvae were run up through increasing 

 grades of alcohol to harden the tissue, remaining in each at least three hours or 

 often longer. Xylol was used as the clearing agent. The otlier method of killing 

 was Tower's Solution, slightly warmed — C12 in 35'/ alcohol 95 parts, glacial 

 acetic two parts, nitric acid three parts — was tried, but the larvae seemed to be 

 too impervious and resistant even to the nitric acid to die quickly. They wriggled 

 about violently for fully five minues, death resulting only after about ten minutes 

 or longer. A combination of the two was then tried, killing them in hot water and 

 then immersing them in Tower's Solution for two hours, then through tiie alcojiols 

 as above. The latter method seemed to yield the best results, when the sections 

 were stained with ]\Iayer's alcoholic carmine. 



For examining the alimentary canal entire and in situ a very good metiiod 

 was found to be the mounting of the entire larva, cleaned, directly in Canada 

 balsam. Slight clouding resulted, but after some time had elapsed it cleared u]) 

 enough to present a beautiful view of the entire alimentary canal. This was 

 supplemented, of course, with transverse and longitudinal serial sections. 



The gullet is large, elongate-ovate, and has at its posterior end a mo\able 

 valve at the entrance to the aesophagus. In feeding, the maggot draws its head 

 in and out rapidly, and at intervals the valve is seen to recede and open the 

 passage to the wsophagus. When the valve opens a black drojilet of oil can be 

 seen to pass down through the (esophagus into the provtntrieulus. 



The oesophagus is long and slender and passes into and traverses completely 

 the proventriculus. The latter is large and s])lierical in shape and lies between 

 the ventricular eaeea?. Between this and the ventriculus, or so-called stomach, then 

 is a deep constriction. Tile ventricular caeca? are four in number, and in propor- 

 tion to the size of the ventriculus are long and ratiier thick. The ventriculus is 

 long, coiled once, thence passes on into the intestine, wliich is long, rather thick 

 and coiled several times. Because of the contents these coils of the ventriculus 

 and intestine are very conspicuous in the live larva, in contrast to the rest of tiie 

 body which is almost transparent. The rectum is somewhat enlarged. The anus 

 is on the venter of the pre-anal segment. Tlie entire alimentary canal pulled 

 out from the .'nius is several times longer than the larva. 



A very striking character of the ventriculus, as seen in section, is the iiii 

 mense size of the epithelial cells and their large nuclei. These cells, in addition 

 to having the large nuclei, are filled witli numerous minute globules, wliieii ar 

 probably the result of the absorption of the oily foods. 



Of four larvas sectioned transversely and eight longitudinally all but one of 

 e.ieli were found to be normal in their digestive canal, except for the large size of 



