186 THK kntomologist's RECORIi. 



fcion, when the full-sized case is quite fresh. Hence, it seems apparent 

 that the species is a biennial one, the larv* going over two winters 

 before the imagines emerge. There are thus two races attaining, in 

 normal conditions of climate, the imaginal stage in alternate years. 



On the following day, after makinj^- the above notes, i.e., on 

 September 28th, I examined other larv;e, taking them from their 

 cases. The first one examined had been out of its case for some days 

 when it was described. 1 found all these others examined were lighter 

 in ground colour, their head and jaws were darker, almost as dark as 

 the plate on the dorsum of the first thoracic segment, the two outside 

 plates on the second segment were better separated from the other 

 two by themselves, and the intersegmental membrane was not so 

 distinct from the ground-colour as in the first one examined. The 

 suggestion is that the first larva examined had darkened from the 

 exposure of several days' duration, and had contracted in size owing 

 to want of food and evaporation from being not protected by the 

 impervious nature of the material of the case. 



Comparison of the various cases at this date showed a few to be 

 more slender, of less diameter, to have a strong ventral ridge, or keel, 

 lighter than the rest of the tube, to be uniformly curved from front to 

 back, and with the anal opening very indefinite and ill-constructed, 

 but apparently only two valved. Possibly these were cases made by 

 younger larvje, or by larvae which had been parasitized or in some way 

 unable to construct a normal case. It was subsequently found that 

 the larva of all these last cases died sooner or later without further 

 completing their dwellings. 



On October 2nd, 1904, 1 found three cases of this species, one ol 

 which was an apparently unfinished case, slender and tapering to the 

 indefinite anal extremity. One of the normal full-sized cases showed 

 three dark longitudinal lines on the ventral side, extending from near 

 the mouth opening to neai" the valves of the anal end. One line was 

 quite central, the others equidistant on each side, a rather curious 

 arrangement, as apparently one suture had been reopened, and served 

 as the suture for the second inserted portion. All three cases showed 

 the remains of the young-time case, i.e., the two halves near the neck 

 of the more mature case. 



The blotches caused by these larva^ on the undersides of the thistle 

 leaves were very numerous, nearly circular, and of small diameter. 

 The larva only protrudes its head and thorax into the mine for a short 

 distance around the hole. In this instance, the leaves of the thistle 

 being luxuriant and very fleshy, and the mines being very numerous, 

 it was easy to see the indications of the presence of larvae without 

 much trouble. Probably the reason that only three larvae were found, 

 although the traces of them were most apparent, was that the date was 

 late in the year, and most had retired into winter quarters, the younger 

 ones to await the spring growth to give renewed life and energies, the 

 older ones to await the time for pupation in late spring or early 

 summer. 



All these larvie were placed on living plants out-of-doors, but only 

 two or three imagines appeared in the July of 1905. The plants died 

 and the cases were ealen by various predatory beasts, which had 

 inadvertently been enclosed in the cage with the earth and the growing 

 plants. 



