ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 75] 



their cases of Char a material. In summer they ascend to the Potamo- 

 geton region and creep about among these, making their cases of small 

 pieces of the leaves. In January they return to the bottom, now using 

 bits of leaves that fall from surrounding trees. 



The material used in case-making is always arranged as a spiral band. 

 The band of the young larva slowly increases in width ; when older, after 

 the last moult, the width remains nearly constant, about 8-10 mm. In 

 building its house the young larva weaves only small fragments of each 

 of the "2-40 mm. long pieces on the case ; later on, when all are of the 

 same length, the whole of each piece is fastened on to the case. The 

 case itself consists of a silken tube, upon which the above-mentioned 

 pieces are fixed. When a fresh piece has to be inserted on the tube, 

 the animal spins a membrane across the angles between the last inserted 

 piece and the former spiral, upon which the new piece is placed. It is 

 then spun together with the preceding one. The contrast of the conical 

 tube of the young larva and the cylindrical tube of the full-grown larva 

 is discussed in detail. 



It seems that the larva makes use of a fixed measure, partly, while 

 the larva is still young, for determining the length of the pieces that have 

 to be inserted on the tube, and partly, in the older stages, for measuring 

 the length of the piece that has to be cut off from the growing plant. 

 The bending-angle of the head probably constitutes this measure, the 

 width of the angle being limited by a peculiar process or horn, project- 

 ing from the under-side of the prothorax — an organ the significance of 

 which has not hitherto been ascertained. It is probably a unit among 

 insects. 



Before pupation the larva fastens itself to the roots of a Garex or 

 creeps into holes in logs lying at the foot of the pond. It rests as pupa 

 from May 15 till June 1. The imago is common on the reeds and rushes 

 in June. 



As to the advantage of the cases described, which are not met with 

 outside the family Phryganidae and the unrelated genus Triseiwdes, the 

 small pieces of leaf arranged in a spiral band encircling the whole case 

 from one end to the other, give the otherwise frail structure the necessary 

 solidity and rigidity. Furthermore, as the material always consists of 

 air-filled pieces of plant, the weight is but slightly increased. And again, 

 owing to their thin and smooth casements, the tubes offer only a slight 

 resistance to the movements of the animals in the water. 



Of all Trichoptera with cruciform larvae, the Phryganidae are the 

 most carnivorous, and at the same time possess greater powers of locomo- 

 tion than the other larvae, which are mainly plant-eaters. The larva? of 

 species of Trisenodes are the only Trichopterous larvae whose tubes are 

 enclosed in material not made by the animal itself, and that, nevertheless, 

 are able to move about and even swim. It thus appears that the spiral 

 construction of the tubes is met with in those Trichopterous larvae which 

 most require light and movable cases. 



Studies on Mallophaga and Anoplura.* — Eric Mjoberg is to be 

 congratulated on this fine piece of work on a difficult subject. In the 

 systematic portion he describes numerous new forms. He then gives 



* Arkiv Zool., vi. (1910) pp. 1-297 (5 pis. and 156 figs.). 



3 c 2 



