Economic entomology for the economicentomolo00smit_0 Year: 1896 STRUCTURE CLASSIFICATION. 31 Fig. I modified for special purposes ; as in some of the piercing insects like bugs or the mosquitoes, where an irritant poison is secreted, or in certain beetles, where the saliva has both a staining and a burning effect upon the skin, or in many larv^ae, where the se- cretion forms a silk when hardened by ex- posure to the air. The anal glands may be similarly modified, but much more rarely than those at the anterior end of the body. In the 'Bombardier beetle' their secretion volatili
Economic entomology for the economicentomolo00smit_0 Year: 1896 STRUCTURE CLASSIFICATION. 31 Fig. I modified for special purposes ; as in some of the piercing insects like bugs or the mosquitoes, where an irritant poison is secreted, or in certain beetles, where the saliva has both a staining and a burning effect upon the skin, or in many larv^ae, where the se- cretion forms a silk when hardened by ex- posure to the air. The anal glands may be similarly modified, but much more rarely than those at the anterior end of the body. In the 'Bombardier beetle' their secretion volatilizes suddenly when expelled into the air, and forms a blue smoke, hke the discharge from a small cannon. In Hymenoptera, including bees and wasps, the secretion is poisonous, and accessory to the functions of the sting. More rarely a silk is produced from these glands. Taken altogether, the digestive system varies greatly in length, being sometimes a straight tube only, the various portions very incompletely divided off In other cases it is quite complex, coiled upon itself, the parts well defined, and the sys- tem as a whole two or three times the length of the entire insect, different kinds of structure being found in the various parts. The figures given herewith illustrate some of these differences. In the sucking or haustellate type the essential structure of the alimentary canal mandible of the same, and the differentiation of the parts are much °^ ^' the same. There is, however, a great reduction in the size of the gizzard, which is very often entirely wanting. If present, the . armature is reduced to a mere ridging, or a slight, irregular thickening of the walls of the posterior end of the crop. In the Lepidoptera there is often a peculiar accessory pouch, which seems to serve the purpose of a storage reservoir, or secondary crop, and this is attached by a narrow neck to the opening of the true crop. In the bees the crop is unusually elastic, and capable Salivary glan
Size: 782px × 2558px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
