57 



on the May gro\\i;h and their work extends towards the base, whereas- 

 that of C. abietis extends towards the tip. The webs of C. arvensis are 

 loose Hke those of C. abietis, but differ in being kept free from excreta 

 and thus resemble those of Acanthoh/da stellata on the pine. The web 

 of C. erythrogastra is very remarkable and constitutes the chief biological 

 peculiarity of this species. When completed, it is a solid tube at least 

 as long as the larva, free from excreta and composed of a dense papery 

 mass of a vivid red-browTi colour. The flight period of these sawflies is- 

 an extended one. The males are on the wing on fine days in April ; 

 mating has been observed as late as the end of July in the case of 

 C. arvensis, while very young larvae of C. eri/throgastm were present 

 at that time. The flight period of C. abietis tends to be restricted to 

 June in mountain districts, probably owing to the shorter summer. 

 These areas are the real habitat of this species, whereas C. arvensis and 



C. erythrogastra occur on the fir both in the plains and in the mountains. 

 The damage they do is usually slight, though a case has been recorded 

 where C. arvensis devastated an old fir forest in Jutland. 



The second section deals with the genus Diprion {Lojjhyrus). Since 

 Hartig's work, this genus had been little studied until Enslin s ex- 

 haustive systematic treatise was published [see above]. Nothing 

 much can be added to Hartig's description of the character of the 

 cocoons of the various species. He appears, however, not to have 

 been aware of the mode of pupation of the non-hibernating larvae of 



D. pallidum, Kl. After living gregariously, they assemble at the tip 

 of the pine twigs and spin their cocoons near the end shoot, thus 

 causing a pecuhar appearance which at once indicates the species. 

 There is still some uncertainty with regard to the larvae of D. virens, 

 KL, D. laricis, Jur., and D. variegatum, Htg. (thomsoni, Knw.). It has 

 been said that those of D. virens and D. laricis are indistinguishable ; 

 but the author disagrees with this, as the D. virens larvae have two 

 distinctly visible, thin, dark, widely separated dorsal lines, while those 

 of D. laricis have only one broad dark line, which only in one portion 

 appears to be slightly divided. In any case, in D. virens the total 

 width of the two narrow lines together with the space between them is 

 greater than the width of the corresponding mark in D. laricis, being- 

 over one-third of the breadth of the back in the former and under one- 

 quarter in the latter. Should these proportions be constant, they will 

 provide an easy means of distinguishing the two species. A further 

 dijB&culty may, however, arise as regards the distinction between 

 D. laricis and D. variegatum. Some account is given of the character 

 of the eggs and the method of oviposition of this genus, though com- 

 paratively little is known about these points. The eggs, especially of 

 D. pini, D. sertifer and D. pallidum, are at times very heavily parasi- 

 tised by what is beheved to be a species of the Chalcid genus Tetra- 

 campe, Forst. According to Borries, this is a general saw-fly egg- 

 parasite and not confined to the species attacking conifers. It is noted 

 that the Weymouth pine is very attractive to D. simile, whereas 

 D. pini can scarcely be persuaded to leave the forest pines (in Germany), 

 and only rarely occurs on the mountain pines growing near by. 

 Observations in the Tharandt district have confirmed the fact that 

 D. sertifer has only one flight period rather late in the year and that it 

 hibernates in the egg-stage, which is not usual ^\^th saw-flies. This 

 species occurs at higher elevations and farther north than any other 



