Our insect friends and foes / by F. Martin Duncan.

  • F. Martin Duncan
Date:
1911
Catalogue details

Licence: In copyright

Credit: Our insect friends and foes / by F. Martin Duncan. Source: Wellcome Collection.

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    circulation and the number of pulsations of the dorsal vessel varies with the atmospheric tem- perature, nearly ceasing at freezing-point. In connection with the classification of insects, there are still many knotty points which can only be conclusively settled by results to be obtained by future embryological research, con- sequently considerable difference of opinion and want of unanimity on the subject exists. How- ever, much has been accomplished, and the once long and arbitrary series of Orders into which the insects were divided have been considerably modified. The insects are now generally divided into the following seven Orders :— 1. Order Coleoptera^ comprising the Beetles, a very numerous group of insects^ possessing two pairs of wings, the front pair (elytra) being horny and dense, meeting in a straight line down the back when closed, and forming a protective case to the membranous posterior pair. The mouth parts are strong and masticatory. The insects go through complete metamorphosis. 2. Order Hymenoptera^ comprising the Ants, Bees, Wasps, and Saw-flies. All the insects included in this Order undergo complete meta- morphosis. This group has generally four mem- branous wings, which in the Bees and Wasps are united during flight by a curious mechanism of minute hooks that engage in a small groove at the posterior edge of the front wings. The Hyme- noptera are divided into two divisions, according to the use of the ovipositor. Thus the Saw- flies, Ichneumon Flies, Sirex or Wood Wasps, and the Gall Flies, who all have the ovipositor
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