Insects. 



8305 



always on Pinus Strobus, and those which I found at Rotterdam in- 

 habited the same species of tree. I have no record of the species of 

 pine on which Dr. Verloren met with his larvae ; it was probably not 

 communicated to me. From the fact of the larvae making their appear- 

 ance in the months of June and September it clearly appears that 

 there are two generations in the year. The usual course is this : 

 the individuals which spin their cocoons about the 1st of October 

 come out in April or May, pair, and deposit their eggs from which 

 larvae are produced, spinning up about the 1st of July ; imagos appear 

 about the end of that month, whose larvae pass the winter in the cocoon. 

 Meanwhile I must here observe that two larvae which had spun up on 

 the 1st of October, 1858, had not assumed the pupa state on the 29th 

 of May, 1859. It is thus very possible that in some years this species 

 produces but one generation, the same as L. Pini. This insect cannot 

 be said to be destructive to our Weymouth pine trees, it having only 

 occurred in the Netherlands sporadically and in small numbers. 



The cocoon of this sawfly, as represented at fig. 3, is of precisely the 

 same shape as that of L. Pini ; it is also equally hard and pergamenta- 

 ceous, but it differs in colour. The cocoons of L. Pini run through 

 a number of tints intermediate between brown and silverygray, those 

 of the present species range from obscure brown to dull yellow, no 

 gray-coloured cocoon being observed. As before stated, the cocoons 

 are found both on the branches and in the moss on the ground. Dr. 

 Wttewaal writes, " The cocoons are attached lengthwise to the branches 

 and also in the angles, this latter position being the most frequent," 

 and makes no mention of their occurrence at the roots, which he thus 

 appears not to have observed. Neither Hartig nor Ratzeburg gives 

 any information as to the place in which the cocoons were found. 



The imago liberates itself by gnawing out a little lid in the same 

 manner as already described* in the case of the other species. I have 

 never been able to observe the pupa ; I have either opened the cocoons 

 too soon or waited too long, as in the case of those I took at Rotter- 

 dam. 



It will be unnecessary to give a particular description of the imago 

 of this species, as was done in the case of the common pine sawfly. 

 It will suffice if we explain the points of difference between the two. 

 It must here, however, be observed that the distinctive characters are 

 not always to be clearly made out, and that varieties of the two species 

 approach each other so nearly that all differences disappear, and the 

 species are no longer to be distinguished. 



Most males of L. similis differ from those of L. Pini in the following 

 VOL. XX. 3 Q 



