594 



Chermes abietis, Kalt., is a common insect in fir woods, even where 

 no larch trees are present. The galls of this species are similar to those 

 of C. viridis, but are of slightly smaller size ; they open later 

 near Petrograd, in the middle and second half of August. The opening 

 galls produce pale yellow nymphs, which moult and produce winged 

 forms ; these remain on the needles of the same fir on which they have 

 bred. They sometimes fly to some other fir trees, but do not migi'ate 

 to larches or other conifers. They are called alatae non-migrantes 

 and each of them deposits a large heap of eggs ; in about two weeks 

 the larvae of the stem-mother hatch and hibernate in cracks of the 

 bark near the base of the buds ; in the following spring the stem- 

 mothers moult and oviposit, the eggs being yellow or yellowish green. 

 Only these two stages exist (fundatrix and alatae non-migrantes) the 

 cycle lasting one year and taking place on firs only. C viridis 

 andC abietis closely resemble each other as regards their morphology, 

 and this has led some authors to consider them as the same species. The 

 author's observations have satisfied him, however, that this is not the 

 case and that they must be regarded as separate species. At the same 

 time, C. abietis can, and sometimes does migrate to and oviposit on 

 larch, pine or silver fir, but the larvae from eggs laid on larches do not 

 survive, nor do the larvae of the spring generation of C viridis from 

 eggs laid on firs instead of larches ; the death of the larvae is due to 

 the fact that the plants are unsuitable for their development ; the 

 proboscis of the fundatrices spuriae is too short to enable them to feed 

 on firs, while those of the fundatrices verae are too long to attack 

 larches. 



The galls of Chennes strobilobius, Kalt., are frequently found in the 

 same places and under the same conditions as those of C viridis, but 

 they are of smaller size and are found exclusively on the very ends of 

 thin branches. The hibernating larval stem-mother lives on the bud 

 itself, not at its base, as do those of the two previous species ; it deposits 

 over 100 eggs, though some of the larvae from these cannot find 

 accommodation inside the galls and perish. This fact, i.e., the presence 

 of larvae on the surface of the galls, is very characteristic both of this 

 species and of C. lappoyiicus, Choi. The galls ripen quickly and 

 open, in North Eussia, in the second half of June or earlier ; the 

 nymphs issuing from the galls produce winged forms, which 

 migi'ate to larches (migrantes alatae) ; there, each of them deposits 

 on the needles about 20 yellowish red eggs from which greenish 

 grey larvae hatch in about two weeks ; these larvae winter in the 

 cracks of the bark, appearing as false stem-mothers (fundatrices 

 spuriae) and in the following spring they pass to the base of the 

 buds, where they moult and oviposit. The great majority of the 

 resulting eggs give rise to dark grey larvae, the skin of which has no 

 glandular lamellae ; these attack the young needles of the larches, turn 

 blackish and moult three times, some of them passing into nymphs with 

 rudimentary wings, while the others moult a fourth time and become 

 clumsy, wingless brown forms, which oviposit on the larch 

 needles and are called exules. The nymphs also moult again and 

 produce winged sexuparae, which fly back to firs. According to 

 Dreyfus and Borner, a small number of the eggs laid by the stem- 

 mother produce larvae the skin of which has the same structure as 

 that of the wintering larval false stem-mother ; these do not develop 



