Zool.— Vol. I.] CALVERT— ODONATA. 411 



of the metathorax, distinctly removed from the abdominal 

 segment, while in Anax Junius, Herpetogomphtis elafis, 

 Pantala hymencea, Tramea onusta, Pseudoleon superbus, 

 Orthemis ferruginea, Dythemis sterilis, Trithemis basifusca, 

 Micrathyria Hageni, Diplax corrupta and Mesothemis sim- 

 ■plicicollis var. collocata (all Anisoptera) the first pair is 

 located in segment 1 or at its articulation with the second 

 abdominal segment. How this difference (which I do not 

 find noticed in the literature) is brought about is yet to be 

 investigated; all young larvae hitherto studied, whether of 

 the Zygoptera or the Anisoptera, have eight abdominal 

 ganglia, located in the first eight abdominal segments. In 

 all the species above mentioned the other six abdominal 

 ganglia of the imago (the imagos have but seven abdominal 

 ganglia) are located as usual in segments 3, 4, 5, 6, 7 

 and 8. 



The study of the gizzard was prompted by the recent 

 publication of Dr. F. Ris' valuable and interesting paper 

 on this neglected organ. 1 



The gizzard, as in other insects, is at the posterior termi- 

 nation of the foregut, where it projects into an invagination 

 of the front end of the midgut, thus forming a valve. It 

 has been stated by previous authors, including the writer 

 and Dr. Ris, 2 that in all the Odonate groups the junction of 

 fore- and midgut lies in the second abdominal segment. 

 Much to my surprise, therefore, I found its position, and, 

 therefore, that of the gizzard, to be very variable, as the 

 following shows: — 



In Hettzrina americana the gizzard was found to lie in 

 the fourth, fifth or sixth abdominal segments in different 

 individuals; in Lestes tenuatus in the sixth; in Archilestes 

 grandis in the fourth or the sixth; in Mecistogaster ornatus 

 opposite the articulation of the sixth and seventh; in Argia 

 agrioides, A. pulla, Erythragrion salvum, and Ischnura 

 Ramburii var \ credula in the sixth; in Anax Junius in the 



1 Zoologische Jahrbiicher, Bd. IX, 1896, pp. 596-624. Summary in Ent. News, February, 

 1897, P- 39- 

 '■< 1 c, p. 606. 



