124 



PSYCHE. 



[October iSg?- 



THE NUMBER OF MOULTS IN INSECTS OF DIFFERENT 

 ORDERS.* 



BY A. S. PACKARD, PROVIDEN'CE, R. I. 



It will be seen from the data here 

 presented that the number of moults 

 is as a rule greatest in metabolic insects 

 with the longest lives, and that an 

 excessive number of ecdyses is due to 

 some ph^'sical cause, such as lack of 

 food combined with low temperature. 



In Campodea there is a single frag- 

 mentary moult (Grassi), while the 

 Collembola i^Afacrototna plumbea) shed 

 their skin throughout life. (Sommer.) 



In the winged insects, especially 

 Lepidoptera, the number of moults is 

 dependent on climate. Insects of wide 

 distribution growing faster in warmer 

 climates consequently shed their skins 

 oftener ; for example the same species 

 may moult once oftener in the southern 

 than in the northern States, as in the 

 case of Callosamia promethea, which 

 in West Virginia is double-brooded. 

 Hibernating larvae moult once oftener 

 than those of the summer brood (Ed- 

 wards) . Weniger by rearing the larvae 

 oi Antheraea tnylitta and Eacles itn- 

 pei-ialis, and which when reared under 

 normal conditions actually have the six 

 stages, when reared in a warm moist 

 atmosphere of about 25° C have but 

 five stages, i. e., moult but four times. 

 In the hot and moist climate of Ceylon, 



* Published in advance from the author's Text book of 

 Entomology, Any corrections or additions would be 

 thankfully received by the author. 



A. tnylitta has but five stages. 

 (Psyche V, p. 2S.) 



Acrydians moult five times; Dia- 

 pheromerafemorata but twice (Riley) ; 

 a katydid {Microcentrum retinervis) 

 moults four times (Comstock). Man- 

 tis religiosa., according to Pagenstecher 

 moults seven times, having eight stages, 

 including that of the singular pre- 

 nymph. Cockroaches {Periplaneta 

 americana) are said b}' Marlatt to pass 

 through a variable number of moults, 

 there being sometimes as many as seven 

 stages. 



In the Homoptera there are in gen- 

 eral from two to four moults ; thus in 

 Typhlocyba there are five stages, in 

 Psocus four, and in Aphis at least three, 

 and in Psylla four during the nymphal 

 state. Riley states that the nymph of 

 the female Coccid, Icerya purchasi, 

 sheds its skin three times and the male 

 twice. Notwithstanding its slow growth, 

 Riley says, the 17-year Cicada moults 

 oftener than once a year, and the num- 

 ber of larval stages probably amounts to 

 twenty-five or thirty in all. The bed- 

 bug sheds its skin five times ; and with 

 the last moult appear the minute wing- 

 pads characteristic of the adult. In 

 Conorhinus sanguisuga there are "at 

 least two larval stages and pupal 

 stages" (Marlatt). 



In the May-fly, Chloeon, the num- 



