The Crane-Flies op New York — Part I 843 



REARING THE IMMATURE STAGES 



As has been stated elsewhere, the author beHeves the most important 

 work yet to be done in entomology is the study of the immature stages 

 of the various groups of insects. In most cases it is necessary to rear 

 the immature stages thru to the adult in order to be certain of the species, 

 and this process of bringing the larva to the perfect condition is often 

 attended with many difficulties. The author has spent several years 

 in rearing the local Tipulidae, and a general statement of the methods 

 adopted is here given. 



It should be borne in mind that the bringing of the larvae from their 

 natural habitat into the warmth of the laboratory accelerates their develop- 

 ment, and the adults emerge in the breeding cages a week or two earher 

 than in nature. 



Aquatic forms 



The aquatic forms are among the most difficult to rear, especially 

 the species living in rapid, well-aerated water. It must be understood 

 at the start that practically all crane-flies require earth, sand, or a similar 

 soHd material in which to pupate, and it is often very difficult to provide 

 rushing torrents for the larval life together with sohd earth for the pupal 

 existence. Breeding cages, consisting of wire cyUnders the ends of 

 which are covered with cheesecloth, have been used with considerable 

 success. The mesh must be of sufficient fineness to retain the larvae 

 inside, but not so small as to exclude the food that is carried in the current; 

 however, since this food is microscopic or very small, a fine mesh is suffi- 

 cient to allow its entry into the cage. The whole cage can be transferred 

 to the natural haunt of the larva and kept imder observation until the adult 

 insect emerges. The main difficulties with this method are the danger of 

 smothering the insect by deposition of silt during high water, the washing 

 away of the entire outfit during storms, and the inconvenience, in most 

 cases, of having to make many long trips to the scene of rearing before 

 the final result is obtained. In almost all cases when the species could 

 be reared by the use of such breeding cages, the writer has been able 

 to get adult flies by placing the full-grown larvae in medium-sized (four- 

 ounce) shell vials together with some earth from their natural habitat. 

 In order to prevent evaporation, small caps of cheesecloth may be fas- 



