Abstract
Abstract The preference for relative humidity (RH) and suitability of different levels of this environmental parameter were investigated in the haematophagous bug Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae). The hygropreference of T. brasiliensis was studied using a RH gradient and the effect of different RHs on the egg hatching, nymph mortality and moulting success was also analysed. The results show that egg hatching in first‐instar nymphs of T. brasiliensis was lower at extreme RHs and, particularly, it was lowest at 9.3% RH. The survival of starved nymphs was not affected by RH, but the percentage of engorged nymphs and the ecdysis success of these nymphs once fed was diminished strongly by high humidity. Fourth‐instar nymphs preferred to stay at the lowest RH during the first 5 days after feeding and during ecdysis. This preference changed markedly during starvation. Fifteen days after ecdysis, the bugs moved towards intermediate humidities, and 30 days after ecdysis they even preferred the most humid sectors of the gradient. Females preferred to lay eggs in dry environments, suggesting that they may not have a particular hygropreference for oviposition, but that they simply lay their eggs at the RHs where they prefer to stay.
Highlights
Trypanosoma cruzi, the aetiological agent of Chagas disease, is a flagellate parasite, which is transmitted by triatomine bugs
The ecdysis success of the engorged nymphs was strongly impaired by the highest relative humidity (RH) (Table 1, Analysis of variance (ANOVA), P
Roca & Lazzari (1994) showed that T. infestans has a strong hygropreference of approximately 0%, which does not depend on starvation
Summary
Trypanosoma cruzi, the aetiological agent of Chagas disease, is a flagellate parasite, which is transmitted by triatomine bugs. Such a disease affects approximately 17 million people in Latin America, where another 100 million people are at risk of contracting it (Schofield & Dias, 1999). Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae) is the main vector of T. cruzi in Brazil. This species can be found in the north-eastern region of this country, in an area characteristically hot and dry, with absence of rain for 8±9 months of the year. Females of this species showed a preference to lay eggs at a low RH (Roca & Lazzari, 1994). Lorenzo & Lazzari (1999) showed that T. infestans prefers experimental shelters with a low RH, and that the natural shelters inside chicken-coops, in a region in which this species is endemic, present RH levels that tend to be lower than that of the external environment
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