18 



Of their natural enemies or parasites none have been observed, 

 though there can be no doubt that various species of ladybirds as well 

 as the larva? of Chrysopids and Syrphids will prey upon them when- 

 ever they become sufficient^ numerous to attract their attention. 



THE GERMAN GRAIN LOUSE. 



(Macrosiphum cerealis Kalt. — Fig. 3.) 



Aphis cerealis Kalt., Monog. d. Pflanzenliiuse, p. 16, 1843. 

 Siphonophora cerealis Koch, Pfianzenlause, p. 86, 1857. 



This species was first described by Dr. J. H. Kaltenbach (Monogr. 

 der Pfianzenlause, p. 16, 1843). At the time he considered it as being 

 identical with Aphis hordei Kyber, which, however, had never been 

 described. 



As food plants the following grains and grasses are mentioned by 

 him: Wheat (Triticum sativum), rye {Secale cereale), oat (Avenafatua 

 and strigosa), barley {Hordeum murinwn), chess {Br omits mollis and 

 secalinus), orchard grass (Dactylis glomerata), velvet grass {Holcus 

 lanatus), and meadow grass (Poa), feeding on the ears, the racemes, 

 the petiole, and occasionally in small colonies on the leaves of grains 

 and grasses, on the former of which, during Juby and August, they 

 may frequently be observed in enormous numbers. 



Buckton (Monog. of Brit. Aphides, vol. 1, p. Ill, 1876), as well as 

 Thomas (Eighth Kept. Nox. and Benef. Insects of 111., p. 51, 1879), 

 make it a synonym of granaria, and the latter author considers it also 

 a synonym of Aphis avense Fab. , neither of them recognizing, how- 

 ever, the characters by which it may be separated from either of them; 

 since then, nobod}^, at least in this country, appears to have taken the 

 trouble to separate the species referred to, notwithstanding that the 

 range of this species appears to be as large as that of the other grain- 

 inhabiting Aphides. 



That both granaria and cerealis are likely to be considered as but 

 one species is very obvious, since both are of about the same size and 

 coloration and may frequently be found intermingled on the same 

 plant, though the maculation of the abdomen of granaria is absent in 

 cerealis, in which the antennal joints and the nectaries are also con- 

 stantly shorter. Divided by tenths, the following variations in these 

 organs will be observed in the present species: 



Antenna! joint 3 varies between 18 and 27. 

 Antennal joint 4 varies between 13 and 21. 

 Antennal joint 5 varies between 11 and 17. 

 Antennal joint 6 varies between 24 and 37. 

 Nectaries vary between 10 and 18. 

 Last fork varies between 13 and 22. 



The above table, compared with that of granaria, shows that, as a 

 rule, all of the measured parts are shorter than those of the species 

 treated of before. 



