98 MISCELLANEOUS PAPERS. 



number of them were reared to the puparium in the trays. The 

 four stages of the maggot were secured by opening some of the cater- 

 pillars from time to time. Thus the entire life-history was worked 

 out for the species, so that now the egg, any stage of the maggot, and 

 the jDuparium as well as the fly can be identified. The entrance of 

 the newly hatched chelonuv maggot into the young clvrysorrhma 

 caterpillar was observed through a binocular microscope. 



It must be stated here that, as a preliminary to the rearing work, 

 the puparia of the various species were carefully studied, and it w^as 

 found possible to identify them by the characters of the anal stigmata, 

 which are very constant in the same form and furnish a variety of 

 design in the various species that was totally unlooked for. By this 

 means the puparia w^ere sorted into species before the issuance of the 

 flies. 



The last stage of the maggot of Parexorista chelonim can always be 

 told by the similarity of its anal stigmata to those of the puparium. 

 The first stage, newly hatched from the egg, is very similar in the 

 various forms of the true tachinids in having the body segments fur- 

 nished wath row^s of minute, posteriorly directed spines, which aid the 

 maggot in jDrogression over the skin of the caterpillar and in entrance 

 through the same. Its anal stigmata are not the same as those of the 

 last-stage maggot. The second stage is characterized by the absence 

 of a large proportion of the spines, especially those of the middle 

 segments, and its anal stigmata begin to look like those of the last 

 stage. The penultimate stage is the most interesting of all, and de- 

 velops an unusual feature, hitherto not understood. The maggot of 

 the first two stages derives no air from the outside, but in the penulti- 

 mate stage it protrudes the pointed anal end through the skin of the 

 caterpillar. This anal end of the penultimate-stage maggot is highly 

 chitinized by virtue of its exposure to the air, and terminates in a 

 pointed tube, which is curved in some species, and within the base of 

 which lie the anal stigmata. Through this extruded tube the maggot 

 l^rocures air. Certain observers had already noted that some tachinid 

 maggots protrude the anal end through the skin of the host, but it 

 was supposed that certain species had this habit in all stages of the 

 maggot, while others had not, since maggots are often found free 

 inside the host. 



The truth, however, is that the penultimate stage of many tachinid 

 maggots, and this stage only, possesses this peculiarity. The last- 

 stage maggots of these species live free inside the hosts, their cast, 

 penultimate-stage, chitinized anal skins remaining in situ in the skin 

 of the caterpillar at the point where they passed that stage. We have 

 rejDeatedly dissected these anal skins from caterpillars containing last- 

 stage maggots. The description of the maggot stages given above 

 applies well to Parexorista clielonice.. A few species, which will be 



