41 Insects and Vegetable Parasites Injurious to Crops The first work undertaken in the laboratories related to this subject, a most important one in the Sudan, and was concerned with the damage done by the so-called “ Asal ” (Honey) fly, which has been found to be a large and new species of Aphis. In 1902 it was very destructive to the dura crop [Sorghum vulgare) in Kassala, Sennar and the Bahr-el-Ghazal. Last summer, (1903), it was not so much in evidence, but the infection of most of the dura grown in Khartoum gave one an opportunity of studying it on the spot, especially in the Zoological Gardens. I do not think that this latter Aphis js the same species as that found on samples sent from Kassala and Sennar. These were very dry and shrivelled, and only a few good specimens were secured. They seemed to be larger than the Khartoum Aphides and had red eyes, whereas those of the Khartoum species were black. The eggs were also different. In Khar¬ toum there was not nearly so copious a secretion of honey-dew, though the leaves were rendered sticky. Differences were also noted in shape. The life history of the Aphides is very complicated, owing to the curious alternation of generations, and unless one be an economic entomologist it is not easy to trace out the various stages and recognise the sexes in the winged and wingless forms. Possibly one stage of the insect’s life is spent on the melon plant. I have had melon plants sent from Rufaa on the Blue Nile with the leaves covered by the Aphis secretion, which often retained the shape of the excreting cornicles and presented a beautiful appearance when viewed through a magnifying lens. These leaves were completely Leaf of Sorghum vulgare, infested by the Aphis sorghi. blighted and the melon crop was ruined. It is, however, probable that this Aphis is yet another species, (for one thing the larvae are very large), and that the others confine their attentions to the dura. They certainly do much damage, sucking out the sap Aphides The “Asal ” fly The melon aphis