Pomona Colleoe Joi-rnal of Entomolooy 6"'1 



Till' lii-nd, MS ill r<-lat<-(l fi)riiis, is ri-tnu-tilc .•mil thus fn|)nl)li- of U-inf; pro- 

 Ifcti-d. Tlic inniitli |mrts arc niiniinl with thi- usual hdoks. and nothiiift tliat is 

 at all ahiiornial. 



Twd int'tli<i(ls Wire followed in studyiiijj the iiitcnial strm-tun- of tin- larva. 

 Ill order to st-c the trac-lital systi-lii clearly, livi- iiia^f;ols were put into iiielte<l 

 trivcerine jfllv directly, thus preveiilinjj the air within the tracheu- from U-inff 

 driven out. The transparency of the liody and the perfect retention of the air 

 witliin (hiiii made the main trachcH" and even the finer net-work of the system 

 he.-iiiti fully distinct ( I'Mgure 'i'i'i A). One straij{lit. continuous tuhe extends from 

 I'jicli posterior spiracle to the correspondiiift »n«' near the anterior end, (jivinp off 

 ill its course numerous hranelies outwardly which branch and n-hranch many 

 times; iM'tween and comu'ctiiiji the two main tubes arc seven arches or loops 

 directed forward, most of which jjive off minute branches at the apex of the 

 .irch forward. Near the base of each main tracheal trunk there is an inferior 

 branch, (piite large, which extends down and forward, one branch evtending back 

 to the anal tij). the remainder (joinp toward the head end, supplying oxygen to 

 the ventral tissu«-s. ."^o far the respiratory system is quite normal. 



If there is anv adaptjitional variation from the normal we would natur.-illy 

 look for it at the entrance to the tracheal trunks, and, in fact, it is just here that 

 we find it. \i the dorsal invaginating fold at the base of the posterior spiraciilar 

 processes the tracheal trunks each turn abru|)tly upward into the jjrocesses. 

 .\bout the middle of the i)rocess the trunk enlarges to form a sub-globose pocket : 

 from this enlargement it extends on to the ti|). o|)eiiing out .it five spiraciilar 

 for.'iinena. or stigmata. 



Transverse an<l longitudinal sections through the tracheal trunks at the 

 posterior end show that the iiitima from the spiracle to the anterior end of the 

 glolMJSc piH-ket is densely lined with long cilia, which apparently s»tvc to strain 

 the air. as it were, by removing the ))articles of dust and oil which might find 

 entrance (Figure i'i'i I)). The spiraciilar openings themselves are ])rotecti'd by a 

 thin, sieve-like, ciliatc cover, easily visible in cross section. Looking at tlii'in 

 from above, i'h situ, they ajijjear as five light pinkish spots on the black back- 

 grouiul, arranged four around a central stigma. As nearly as can 1m- determined 

 this cover consists of many cilia r.-idiating from the circumference. No tr.aces of 

 a valve or of occlusor muscles are visible, and this is readily explained by tin- 

 substitution for tlit-se of the telescoping of the entire stigma. 



The anterior spiracles arc- much smaller, less conspicuously chilini/ed, and 

 situated well forward near the ))Osterior c-nd of the head. These also an- ri-trac- 

 tile. but, as already described, diffi-rt-ntly from the posterior |)air. As in tlii- 

 others the tracheal trunk enlarges abruptly into a largt- sac near the surface and 

 thence continues to the surfaci- in tin- form of a slend<-r, thickly chitinized tiibi- 

 whieh exp.-inds at the tip into a large c.-ipiit with a number of fncet-liki- stigmata. 

 Inti-rn.-illy the sac and tube an- lini-d with cilia, as in the case of the posterior 

 . tracheu-. F.xtending in as far as the base of the tracheal sac is an invagination 

 of till- ciiticular wall. When the spiracles are extended for bn-athing. the invag- 

 ination is eontiiuuil outward in .-in evagination to the base of the tracheal caput. 



