LIFE HISTORY OF THE COMMON SQUASH BUG. 21 



1883 (1884, pp. 119, 120), figures and describes four stages of the tar- 

 nished plant-bug, Lygus pratensis. Of the different stages of the cotton 

 stainer, Dysdercus suturellus, Messrs. Biley and Howard remark in 

 Insect Life (vol. I, p. 236), that among the material sent to the Depart- 

 ment four preparatory stages were distinguished, " which undoubtedly 

 represent separate molts, and, from the gradation in size, probably 

 represent the complete life of the insect." These four stages are illus- 

 trated, as also what is doubtfully believed to be the newly hatched 

 nymph. Other instances of the recognition of four nymphal stages 

 might be cited, but the above will serve to define the trend of opinion 

 on this topic until recent years. 



In none of the works consulted, except those of comparatively recent 

 date, did the writer find mention of the occurrence of more than four 

 stages in the growth of Heteroptera, except in Mr. M. V. Slingerland's 

 bulletin on the four-lined leaf-bug (Bui. 58, 0. IT. Agl. Expt. Sta., Oct., 

 1893), and in Mr. A. L. Quaintance's bulletin on strawberry insects 

 (Fla. Agric. Exp. Station, Bui. 12, August, 1897, pp. 566-574). In the 

 former bulletin five stages of the Oapsid, Poecilocapsus lineatus, are fig- 

 ured and described, and in the latter, Pamera vincta, a small Lygaeid, 

 is similarly treated. 



At the opening of the season of 1898 an attempt was made to find 

 a sufficient number of the adults of Anasa armigera to observe all the 

 differeut stages and molts. As this effort at first met with failure, it 

 was determined to make the same experiment with A. tristis. As a 

 result, five distinct stages, in addition to the egg and adult, were 

 observed. Later the same five stages were recoguized in A. armigera. 

 It is somewhat surprising that the existence of these five stages were 

 not known to earlier writers. This may be accounted for in most cases 

 perhaps by the failure to recognize a difference between the second 

 and third stages and less frequently between the third and fourtb. 



Some zoologists, among others Messrs. Oomstock and Quaintance, 

 consider all of the immature active stages of Heteroptera as nymphs. 

 On the assumption that the difference between the larvre and the 

 nymphs consists in the absence or presence of wing-pads, it is often a 

 matter of considerable difficulty to separate the one from the other. 

 According to this definition, the stage just previous to the last molt 

 before the adult stage is assumed is always a nymph, as is also the 

 stage just previous to this, but the two stages between this last and 

 the first, or so-called larval stage, are difficult to define. Practically all 

 stages in some species have either wing-pads or at least the semblance 

 of them. 



It should be remembered that the descriptions and measurements 

 that will be given of Anasa tristis apply to the nymphs immediately 

 after molting, this being the time taken for the descriptions. There is 

 practically no difference between the length of the body just before 

 and immediately after molting. 



