He then carefully removed the œsophageal diverticula with their content of yeast and introduced them into an opening in the skin of the hand. Within a few seconds there was noticeable the characteristic itching irritation of the mosquito bite; and in a short time there appeared reddening and typical swelling. This was usually much more severe than after the usual mosquito bite, and the swelling persisted and itched longer. This was because by the ordinary bite of the mosquito most of the yeast cells are again sucked up, while in these experiments they remained in the wound. These experiments were repeated a number of times on himself, his assistant and others, and always with the same result. From them Schaudinn decided that the poisonous action of the mosquito bite is caused by an enzyme from a commensal fungus. These conclusions have not, as yet, been satisfactorily tested. Relief from the effect of the mosquito bite may be obtained by bathing the swellings with weak ammonia or, according to Howard, by using moist soap. The latter is to be rubbed gently on the puncture and is said to speedily allay the irritation. Howard also quotes from the _Journal of Tropical Medicine and Hygiene_ to the effect that a few drops of a solution of thirty to forty grains of iodine to an ounce of saponated petroleum rubbed into the mosquito bite, or wasp sting, allay the pain instantaneously. Methods of mosquito control will be discussed later, in considering these insects as parasites and as carriers of disease. STINGING INSECTS The stinging insects all belong to the order HYMENOPTERA. In a number of families of this group the ovipositor is modified to form a sting and is connected with poison-secreting glands. We shall consider the apparatus of the honey-bee and then make briefer reference to that of other forms. APIS MELLIFICA, THE HONEY BEE--The sting of the worker honey-bee is situated within a so-called sting chamber at the end of the abdomen. This chamber is produced by the infolding of the greatly reduced and modified eighth, ninth and tenth abdominal segments into the seventh.[D] From it the dart-like sting can be quickly exserted. The sting (fig. 25) is made up of a central shaft, ventro-laterad of which are the paired _lancets_, or darts, which are provided with sharp, recurved teeth. Still further laterad lie the paired whitish, finger-like _sting palpi_. Comparative morphological as well as embryological studies have clearly established that these three parts correspond to the three pairs of gonopophyses of the ovipositor of more generalized insects. [Illustration: 25. Sting of a honey bee. _Psn Sc_, base of acid poison gland; _B Gl_, alkaline poison gland; _Stn Plp_, sting palpi; _Sh B_, bulb of sting; _Sh A_, basal arm; _Lct_, lancets or darts; _Sh s_, shaft of sting. Modified from Snodgrass.] [Illustration: 26. Poison apparatus of a honey bee. Modified from Snodgrass.]