PACHYTHELIA VILLOSELLA. 405 



the larva draw itself entirely within its case and to remain quite still 

 for a considerable period. Hofmann notes that when full-fed, the male 

 larvae spin up on grasses, &c, at the foot of tree-trunks, the female 

 larva? usually from 2ft. -4ft. up the trunks. 



Larva. — The young larva of P. villosella (in its first hybernating stage, 

 October 8th, 1899) is about 6-5mm. in length, l-5mm. in width, and 

 under the microscope shows traces of the pale markings on face and 

 thorax that characterise the adult larva, and also the dark anal plates. 

 To the naked eye, however, the abdomen is reddish-brown and the 

 head and thorax black, the body is flatter and wider relatively than 

 that of A. opacella, and the lateral flanges are more prominent than in 

 that species. The central depression of the prolegs do not appear to be 

 corneous, and the spiracles are much less noticeable than in A. opacella 

 (Bacot). The fullgrown larva has the head black, with several whitish 

 marks on face, and many hairs ; the pro-, meso- and metathorax 

 black, corneous, with whitish mediodorsal line, and much wider 

 whitish-yellow subdorsal lines extending to the 3rd abdominal seg- 

 ment. The abdomen dirty blackish-grey in colour, the 1st, 2nd, and 

 3rd abdominal segments rather darker than the following ; the 

 subdorsal lines of the thoracic segments exist on lst-3rd abdominal 

 segments as creamy-white spots ; a triple lateral flange, dirty white in 

 colour, extends the whole length of the abdomen, weakened after the 

 6th abdominal ; the upper ridge most developed, but all broken by the 

 strongly-marked, abdominal, segmental incisions, the upper ridge (of 

 flange) continued on thoracic segments, but black (thus taking on the 

 colour of the chitinous covering of the thoracic segments) . The abdominal 

 spiracles dark and conspicuous on whitish ground colour, situated 

 almost in groove between 1st and 2nd lateral ridges rather anterior to 

 the middle of the segment. The true legs black, corneous, the joints 

 pale, and a single strong terminal hook ; several hairs at joints. The 

 prolegs strong, the crochets forming a somewhat elongated oval (the 

 inner edge without hooks) from 26 to 30 in number (in one case 24 on 

 one side and 30 on the other) ; the anal prolegs somewhat close 

 together, each with 28 short and very strong hooks. The ventral area 

 dirty yellowish-Avhite like the lateral flanges and, therefore, much 

 paler than the dorsal area. On the abdominal segments are dorsally, 

 on either side, two black marks, which are deeper portions of the 

 groove marking the subsegments ; on 7th abdominal a distinct black 

 spot occurs before the inner of these, but is really part of it, if one 

 may judge by the preceding segments. On the 4th, 5th, and 6th 

 abdominal segments the trapezoidal tubercles are reversed (i.e., i 

 farther from mediodorsal line than ii), these are small pale plates, with 

 very minute bristles, ii being just posterior and slightly outside the 

 inner black mark noted, the exterior, i, is a good way in front of the 

 outer of the black marks ; on the forward segments these become 

 gradually larger, and on the 1st abdominal they form large lunular 

 marks ; on the 1st and 2nd abdominals also they are supplemented by 

 a similar plate at posterior margin of segment, and behind i, but this 

 is without a hair. The triple lateral flange has the three ridges (and 

 a smaller subsidiary one) separated from each other by shallow grooves, 

 but above and below are deeper ones ; the upper of these ridges is the 

 larger and carries above it a large oval plate, with a hair, iii, towards 

 its anterior end ; below this, and rather on the prominence of this 



