308 



rapidly. After the harvest, and until the germination of the fallen 

 grain, the aphids apparently feed on the remnants and waste of the 

 harvest, although according to Mokrzecki they then live on grasses 

 such as Hordeum rnurinum, etc. The practice of some small farmers 

 of mowing a part of the barley while still green for forage leads to the 

 appearance of seedhngs from fallen grain at the time of the harvest, 

 and assists the aphids at this time. In the first half of October the 

 sexual forms appeared and were observed in the open up to the first 

 frosts, the resulting eggs hatching in the following spring. 



The influence of physical conditions on these aphids is nexl, dealt 

 with. A temperature of 75° F. to 100° F. is required for their develop- 

 ment, a decline and especially a rise in the thermometer proving fatal 

 to them. A temperature of over 100° F., accompanied by dry winds, 

 produces a death rate of 75 per cent. Wind has a greater importance 

 than moisture, owing to the increased effects of temperature it produces 

 and also to its influence on the distribution of the winged forms. 



The following natural enemies of B. noxius are recorded : — Limothrips 



cerealium, Naly., and Haplothrips tritici, Kurd., which cause a folding 



of the sheath-leaf in the same way as the aphids and often seem to 



drive the latter from the plants. The author has not been able to 



verify the statement of A. Mordwilko that Anthocoris sp. were present 



in the leaves infested with aphids. Two species of Chrysopa were 



observed in the aphid colonies, the larvae, which are mostly found in 



June and July, destroying large numbers. Coccinella 7- punctata and 



C. l4:-piinctata were observed destroying the Uce, especially in June 



and July. The larvae of the Syrphid, Sphaerophoria (Melithreptus) 



scripta, were found in June and July in the colonies of B. noxius, 



devouring large numbers. From the puparia of these insects the 



hymenopterous parasites, Homotripus signatus, Grav., Encyrtus aphi- 



divonis, Mayr, Pachyneuron sp., and a parasite resembling the 



Ichneumon, Bassus laetatorius, though distinct from it, were obtained. 



The Chrysopa larvae also devoured those of S. scripta. The larvae of 



Syrphus auric^llis and S. anmdipes, which also feed on the aphids, 



are parasitised by Bassus laetatorius. Leucopis argetitata, Heeg., was 



specially active during the time the Uce have to feed on the remnants 



of the harvest ; from the puparia of these insects Xana nigra, Kurd., 



sp. n. (subfamily Aphelininae) was reared, but apparently the parasite 



is not of great importance. Aphelimis hordei, Kurd., often infested 



whole colonies of B. noxius. Imagines were obtained on 28th August, 



the males emerging from undersized individuals and females from 



large ones. Some importance is attached to a small, unidentified spider 



which lives inside infested ears and weaves its web round the spikes. 



It not only destroys several aphids a day, but the web prevents their 



migration. In the absence of experiments on remedies against this 



pest, the author is only able to suggest general methods tending to 



improved cultivation, such as timely ploughing and sowing, care 



during harvest, removal of seedlings from fallen grain on roads 



and fields, early harvesting when the grains are still firmly attached 



to the ear, manuring with mineral manure, rolling and harrowing 



infested fields, trap-crops combined with grazing cattle, black fallow 



in winter, etc. Spraying, although useful when the aphids are exposed, 



cannot be recommended, being too costly. A hst of 14 works on the 



subject is given ; 12 of these are Russian. 



