THE ENEMIES OF THE PINE AND SPRUCE AMONGST THE MICROLEPIDOPTERA XXV 



as the feeding habits were the same, it is very likely that the number of ge- 

 nerations in both species is also the same. Dvscedestis fatinatella was far 

 niore scarce in the material reared than Ocnerostoma. Details of the last instar 

 are given in fig. 39, of the last but one in figs. 40 and 41, and the cocoon 

 is reproduced fig. 42. 



Oc7ierostoma piniariella Zell. The egg is laid at the top of a needle (ä, fig. 

 44 d), generally at the concave side. The gallery is at first very narrow 

 (mg, fig. 44 d) and avoids the central part of the needle, (m, fig. 44 b)^ but 

 after a distance of 10 — 12 mm. it occupies the whole interiör of the needle, 

 leaving only the epidermis and the hypodermis unattacked. The gallery is 

 about 40 mm. long, and the larva leaves the needle through a hole near its 

 base (u, fig, 44 a). A needle mined by Ocnerostoma (or Dyscedestis) is charac- 

 terized by the following features: at the top the egg-shell as a rule remains, 

 a part of the mine, about 20 mm. long, is filled with densely packed excre- 

 ment (e, fig. 44 d), and below this a part, about 9 mm. long, is empty, 

 having been occupied by the larva before leaving the mine. When the larva 

 has left the mine it attachés itself firmly to a needle (fig. 46 b) and changes 

 its skin, the last instar not feeding but only spinning together 4 — 6 needles into 

 a tube, wherein the pupation takes place (fig. 46 c). The development takes 

 the following course: early in spring hibernating larvae are found in the 

 needles, but already by about the 2oth of April many larvae had left the 

 mines and were found attached to the needles or suspended from them. After 

 the 2oth of May no larvae were seen, and in the middle of June the moths 

 appeared. After this there is a gap in my observations, but on the i5th of 

 July a new generation of larvae was noticed, and in the same locality on 

 August 1 8th newly hatched larvae were found, in all probability forming the 

 second generation, the larvae of which were subsequently found throughout 

 the autumn and the winter, e. g. on December the 1 2th at Nynäs and in 

 the beginning of February at Karlsborg. At the latter place the author had 

 the opportunity to notice that the larvae do not pass the winter in a state of 

 lethargy, but feed whenever the temperature rises enough to allow it, +4.5^0 

 being quite sufficient for the larvae to start feeding! 



Details of the last but one instar of the larva are given fig. 47 and 48 and 

 of the pupa fig. 49. 



Parasites of Ocnerostoma. As already mentioned in a previous paper (VI) 

 many of the larvae were parasitized by Ageniaspis fuscicollis Dalm, a species 

 which has polyembryonic development. 



Comparison behveen the spruce-needle atid pme-7ieedle tn/iiers. 



The difference in size of the spruce and the pine needles has greatly in: 

 fiuenced the biology and morphology of the miners. VVhile the former is too 

 small to furnish a larva with food during its whole development, the latter 

 has an ample supply, and not less than three species, Cedestis gysselhiella, 

 Dyscedestis farinatella and Ocnerostoma pifuariclla dejiend during their growth 

 on a single pine needle. As a consequence the spruce-needle miners must 

 wander between the needles in order to get sufi"icient food, whereas the pine- 

 needle miner only leaves the needle in order to undergo the last ecdysis. 

 This difterence in habits has put its stamp on the morphology of the larvae. 

 In the three ])ine-needle miners there is a pronounced difference between 

 the last instar and the other ones, which does not exist in the spruce-needle 



