and Laboratory Methods. 1467 



ware stores, and may be purchased cheaply. In bringing larvae and pupae in 

 from the field, too much jarring about in a bottle may result in their death by 

 drowning. It is desirable, therefore, to put moss or water-weed in the bottle 

 with a minimum of water, provided the insects are transferred to an aquarium or 

 a still jar within a few hours. 



Nuttall, Cobbett, and Strangeways-Pigg, who have done a great deal of col- 

 lecting of mosquito larvae in England, as shown in one of their important papers, 

 entitled "Studies in Relation to Malaria," published in Xho^ Journal of Hygiene, 

 Vol. 1, No. 1, January, 1901, used as their collecting apparatus some wide- 

 mouthed bottles of medium size with cork stoppers ; a white enamelled dipper 

 which, when required, can be tied with a piece of twine to a long bamboo rod ; 

 a small pipette with a rubber bulb, and small vials containing dilute alcohol for 

 the preservation of larvae which they did not wish to keep alive. They travelled 

 over England on their collecting trip on bicycles. When the larvae or eggs were 

 captured in the porcelain dippers they were removed with a pipette and put in 

 bottles, which were half filled with water, wrapped in cloths, and attached to the 

 bicycle frame. They found that they could be transported for several hours 

 without injury. They noted also that the large larvae did not withstand the 

 shaking as well as the small ones, but that a sufficient number could always be 

 brought back for studying purposes. On expeditions lasting a couple of days, 

 they took precaution to remove the corks occasionally to give the insects fresh 

 air. White dippers were used, since they could more easily detect the eggs or 

 larvae on the white background, and they found that only rarely could they 

 detect the insects by direct inspection of the surface of the water. 



Larvae and pupae, when it is desirable to preserve them in these stages, and it 

 is always desirable to keep a small set of each species, may be kept in vials of 

 alcohol or dilute formalin (5 to 10 per cent.). When preserved in alcohol they 

 should be passed through different strengths, beginning with a weak mixture, in 

 order that they may not shrivel ; or, what is still better, kill the larvae or pupae 

 suddenly in a cyanide bottle, then bring the water nearly to the boiling point in 

 a little porcelain dish over an alcohol lamp, and drop the insects in, leave them 

 until the boiling point is just reached, and then remove them. An immersion of 

 only a few moments will suffice. Ordinarily the larvae will sink at once to the 

 bottom of the water, and very soon thereafter rise to the top. This rising is an 

 indication that the specimen should be removed at once. The specimen may 

 then be preserved in ordinary commercial alcohol, and will retain perfectly its 

 color and shape. This method is used successfully with the larvae of many 

 insects. It is not necessary to mount either larvae or pupae whole on slides. 

 One of these preserved specimens can be put in a cell with alcohol or glycerin 

 and studied under a low power with perfect ease, and the examination of minute 

 details of its anatomy, external and internal, may readily be accomplished by 

 dissection, and the parts dissected out mounted permanently on slides in any of 

 the ordinary media. 



In rearing different species of mosquitoes I have had perfect success in the 

 use of large, cylindrical glass jars, known as battery jars. They can be bought 

 in almost any city, and of various sizes. The size which I find most convenient 

 will hold about a gallon of water. A layer of sand an inch or two deep is placed 

 in the bottom of the jar and a quart or more of water poured over it. After the 

 sand has settled and the water has cleared, a bit of almost any small water-plant 

 may be inserted to advantage, provided mosquitoes of the genus Culex are being 

 reared. If the experiment is with Anopheles, however, some fresh-water alga is 

 introduced, such as Spirogyra, Mougeotia, OEodogodium, Cladophora, or Oscil- 

 laria — almost any green scum from stagnant water, in fact. Over the top of the 

 jar is placed a piece of swiss, or other fine, translucent cloth, held down by a 

 large rubber band. 



