SOUTH AFRICAN BAGWORMS. 661 



to enclose the larva. With subsequent growth the bag is 

 enlarged and from conical becomes oval, that is, wide in the 

 centre and narrow at each end. The space inside is now 

 larger than the volume of the larva requires. The manner 

 in which the change in the form of the bag is brought about 

 we have not been able to observe. As the larva feeds, 

 particles of the leaves and twigs are being thrown back and 

 attached to the neck of the bag for a short distance. No' 

 regularit}^ is observed except in so far that all these particles 

 are attached lengthwise, and, as they are fastened for a short 

 distance only, they project tangentially in the direction of the 

 long axis of the bag. During the feeding they are loosely 

 attached. The firmer attachment is probably accomplished 

 during the night, as in order to do this the larva will have to 

 expose itself for a considerable distance, and it may in some 

 cases even be necessary for it to leave the shelter of its bag. 

 Everything which may be attached to the branch or leaf,, 

 such as seed-pods, parts of twigs, even other pieces of insect 

 architecture are indiscriminately made use of, and the result 

 is at times a very curious mixture of ingredients. 



According to the plant on which the bagworm is feeding, the 

 composition of the bag-covering, and thus its aspect, varies 

 considerably, but the oval shape and the partial longitudinal 

 attachment of the component particles are constant characters. 



Toward the later instars the differences between the male 

 and the female bags become apparent ; the bag of the 

 female is large and plump, while that of the male is shorter 

 and has a longer point, but it is not relatively narrower.. 

 These differences are not absolute, since according to variations 

 in food-supply we may find small females and lai'ge males, 

 and it is therefore not always possible to judge with certainty 

 from the appearance of the bag the sex of its occupant. 

 Measurements of several hundreds of bags, containing mature 

 larvae, gave the following results : 



Male bags: Average length 46*95 mm., width 17-32 mm. 

 Maximum length 56 mm., width 21 mm. 

 Minimum length 39 mm,, width 15 mm. 



