^192 Pomona College Journal of Entomology 



N^'lifii thf spiracles are retracted, tlur tracheal tube between the sac and caput 

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

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

 like, ciliate membrane. 



The other method used in tiic 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 the body and preventing its contraction. After 

 being in the hot 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 other method of killing 

 was Tower's Solution, slightly warmed — C12 in 35 9( 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 the alcohols 

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

 were stained with Ma3'er's alcoholic carmine. 



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

 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 up 

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

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



The gullet is large, elongate-ovate, and has at its posterior end a movable 

 valve at the entrance to the asophagus. 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 oesophagus. When the valve opens a black droplet of oil can be 

 seen to ))ass down tlirough the cesophagus into the proventriculus. 



The (esoi)hagus is long and slender and passes into and traverses completely 

 tiie jjroventriculus. The latter is large and spherical in shape and lies between 

 the ventricular caecae. Between this and the ventriculus, or so-called stomach, there 

 is a deej) constriction. The ventricular ca>c* are four in number, and in propor- 

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

 long, coiled once, thence passes on into the intestine, which 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 the 

 body which is almost transparent. The rectum is somewhat enlarged. Tlie .uius 

 is on the venter of the pre-anal segment. The entire .ilimint.iry ean.il pulled 

 out from the anus is several times longer than the larva. 



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

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

 to having the large nuclei, are filled witii numerous minute globules, whieli ar.' 

 probably the result of the absorption of the oily foods. 



Of four larvw sectioned tr.-insversely and eight longitudinall}' all but one of 

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



