Table S1. Responses of the Survey on Prolonged Nymphal Development

Table S1. Responses of the survey on prolonged nymphal development.

Name and Response Species involved Possible explanations Institution 1. Cleber Galvão, Observed so-called “extranumerary 5th Observed fortuitously, but Possibly related to a disorder in the juvenile hormone Instituto Oswaldo stage nymphs” (nymphs V that molt, several species are involved. and the ecdysone. A subject worth investigating. Cruz, Rio de but continue as immature until they die Janeiro, Brazil. many months later). Never observed in other nymphal stages. 2. Carlos Eduardo Observed the phenomenon of T. rubrovaria Postulated two possible explanations: (i) a strategy to Almeida, Instituto “developmental arrest”, more clearly T. maculata avoid the imaginal molt during the cold season, that Oswaldo Cruz, when the temperature drops down. Also T. pseudomaculata could spoil reproduction, (ii) an inbreeding process in Rio de Janeiro, observed that it happens in other stages T. infestans laboratory colonies (a sort of “lethargy” mainly after Brazil. (but not so significantly). Deformed T. circumaculata the 2nd laboratory generation), and correlated with a specimens that had tried to molt were T. brasiliensis higher mortality and lower fertility. Mentioned that seen. In Triatoma rubrovaria most of other species (T. infestans, T. brasiliensis and stage V nymphs that delayed to molt Rhodnius prolixus) can be reared for more generations ended up doing it. Some individuals without showing these effects. created a really hard skin and thought they would never molt, but most of them did. 3. Ricardo Observed this many times, and T. infestans Thought it could be a virus, but could never confirm Gürtler, considers it not rare at all, but restricted this. Considered it may be related to a lack of adequate Universidad de to nymphs V. symbionts, but for colonies where the bugs are reared Buenos Aires, in groups he considers this as completely impossible. Buenos Aires, Argentina. 4. David Gorla, Observed delays in nymphs V, but T. infestans Asks: is there some genetically pre-programmed Centro de never paid attention (considered them characteristic as a strategy of spreading the risks? Investigación as “idle” bugs). Some nymphs V took Científica y de so long to molt that he had to discard Transferencia them because it delayed his Tecnológica, La measurements. In field experiments in Rioja, Argentina. monthly censuses nymphs V never molted 100%, while nymphs IV were usually near 100% [1]. 5. Silvia Does not recall that some nymphs V did T. infestans No explanation. Pietrokovsky, not molt into adults, because normally T. guasayana Universidad de they all molted “sooner or later”. Buenos Aires, Buenos Aires, Argentina. 6. Julieta Nattero, Not working any more with Not given. No explanation. Universidad triatomines, but recalls having observed Nacional de a slower development in some nymphs Córdoba, V (and not in other developmental Córdoba, stages). Argentina. 7. José Jurberg, Observed a slower development in Panstrongylus geniculatus Inadequate rearing conditions, such as temperature, Instituto Oswaldo some nymphs (V and other stages). humidity, and diet. A nymph V of P. geniculatus took Cruz, Rio de 261 days to reach maturity because of low humidity. Janeiro, Brazil. 8. Mario Steindel, Observed delayed molting, particularly P. megistus Some feeding or other physiological problems. Universidade in nymphs V, but also in other T. infestans Discussed this with Dr. Schaub (Germany) who Federal de Santa development stages. More frequent R. prolixus believes that it could be related to a lack of symbionts. Catarina, with P. megistus, and in some cases the R. domesticus Florianópolis, nymph V could remain in that stage for Brazil. more than 6 months. 9. Carlota Observed a “developmental arrest” in T. dimidiata A mechanism limited to a few individuals allowing Monroy, the laboratory and in the field in T. them to remain for a long time in a given Universidad de dimidiata, mainly in nymphs V. One developmental stage until something triggers the San Carlos, nymph V individual of T. dimidiata change, and then molt to adults or die. Guatemala City, under sylvatic conditions remained Guatemala. without molting for four months while the rest of the nymphs V had all molted in less than two months. 10. Felipe Guhl Never had an experience of Suggests to investigate if insect collected in the field Nannetti, “developmental arrest”. are not parasitized by T. rangeli. Universidad de Los Andes, Bogotá, Colombia. 11. Marlene Observed the “developmental arrest”, P. geniculatus In T. ryckmani larger nymphs may “wait” for smaller Cordero and but always staying as nymphs V, not R. pallescens nymphs to feed on them *. In P. geniculatus and R. Rodrigo Zeledón, molting to adults, despite they feed T. ryckmani pallescens it may be the result of the anesthetization of Universidad well. the host. Nacional de Costa Rica, Costa Rica. 12. Vera Lúcia Observed frequently that some nymphs P. megistus Result from an incomplete feeding, making difficult Cortiço Corrêa V and nymphs of other stages do not T. infestans the abdominal distension, that triggers the cerebral Rodrigues, molt and remain in their stage for a hormone that induces the molting. SUCEN, Sao long time, some of them dying without Paulo, Brazil. being able to molt. Some nymphs V seem to “pass” to another stage which she calls nymphs VI or “adultoids”, for they have some adult features but are wingless. 13. José Alejandro A “development arrest” in nymphs V T. mexicana No explanation. Martínez Ibarra, takes place with relatively high T. dimidiata Universidad de frequency. In T. mexicana he had about T. rubida Guadalajara, 200 nymphs V for more than seven T. barberi Jalisco, Mexico. months. About (around 5-10% end up and species of the Meccus molting to adults). Very variable: some phyllosomus complex. individuals never feed; others feed but although engorged they die. 14. Hugo Antonio “Developmental arrest” in nymphs V T. dimidiata The result of nymphs V being "bellyful" Ruiz Piña, takes place with relatively high (“empachadas”). Universidad frequency, in particular when feeding Autónoma de with many nymphs per flask. Yucatán, Mérida, Mexico. 15. Elena Has seen this “developmental arrest”, T. patagonica No explanation. Visciarelli, mainly in nymphs V, but with very low Universidad frequency. She detected nymphs V with Nacional del Sur, short and long cycles of development. Bahía Blanca, Argentina. 16. Elis Aldana, Observed “developmental arrest” in In various species but “Developmental arrest” is a trait with adaptive value; Universidad de nymphs V (also in nymphs I, II and III especially R. prolixus. we should measure the pattern of expression of this Los Andes, but less frequently). A small number of behavior under different conditions with individuals Mérida, individuals do not reach the adult stage, from the same cohort (“reaction norm”), and that we Venezuela. even if a source of food is offered should look for a “trade off” between the frequency of periodically. individuals with this trait and the survival of adults. He suggests to look into the distribution frequency of individuals of different stages in different times of the year. 17. Luis Fernando Observed “developmental arrest” in P. geniculatus and various Results of a problem of nutrients/micronutrients (type Cháves, Emory nymphs IV and V. species of Triatoma. of host blood) or a problem of hybrid lines. It might be University, a problem of trade-offs in life history. Atlanta, Georgia, USA. 18. Maria Dora Does not recall clearly, only a higher Not given. No explanation. Feliciangeli, mortality in nymphs V. Universidad de Carabobo, Maracay, Venezuela. 19. Pedro Cattan, Confirms “developmental arrest” in Mepraia spinolai Result of laboratory feeding with chicken blood. Universidad de nymphs V. Sometimes almost one year Chile, Santiago, before molting to the adult stage. Chile. 20. Claudio Confirms “developmental arrest” in T. infestans Suspected of Blastochrytidia but had to be eliminated. Lazzari, nymphs V. They remain for “months Primary cause not known but in the last instance it Université and months” despite feeding normally. manifests as a hormonal. François Rabelais, Tours, France. 21. Claudia Between 3-10 % of nymph V were in T. infestans and No explanation. Rodríguez, “development arrest”. A relatively high T. patagonica Universidad proportion (50-80%) molted into adults. T. platensis Nacional de Between 50 and 80% of rearing flasks T. guasayana (possibly) Córdoba, showed at least an individual with Córdoba, “arrest” during a 6-12 months period of Argentina. normal rearing. In T. guasayana “development arrest” depended on the season or time of the year. Various nymphal stages initiated it from April to August-September. No difference in sex-ratio was observed in the slow developing nymphs. * This phenomenon has been called "kleptohemodeipnonism" [2].

References 1. Gorla DE (1991) Recovery of Triatoma infestans populations after insecticide application: An experimental field study. Med Vet Ent 5: 311–324. 2. Ryckman R (1951) Recent observations of cannibalism in Triatoma (Hemiptera: Reduviidae). Journal of Parasitology 37: 433–434.