J. Ent. Acar. Res.
Ser. II, 42 (3): 153-160

30 December 2010

L. LIMoNTa, J. SULo, D.P. LoCaTeLLI 

Temperature-dependent development and survivorship of Idaea inquinata 
(Scopoli) (Lepidoptera Geometridae) eggs at two humidity levels

Abstract - Idaea inquinata (Scopoli) mainly feeds on dried plants, nevertheless, it 
is also a potential pest of stored product as it is able to develop on cereal products. 
The few references on the biology of this species do not deal with the influence of 
temperature and relative humidity on egg hatching. To fill this gap, groups of 100 
eggs, 24-48 hours old, were exposed to constant temperatures (13, 15, 36, and 38±1 
°C), two relative humidities (35, 70±5%) and a photoperiod of 0:24 (Light:Dark); 
eight tests were carried out. each test was replicated four times. The lowest propor-
tion of hatched eggs was observed at 15 °C (9.5) and 36 °C (8.7) with 35±5% r.H. 
while at 13 and 38 °C eggs did not hatch. a non-linear function is used to represent 
the developmental rates and survivorship of eggs at 35 and 70% r.H. between lower 
and upper thresholds temperature. 

Riassunto - Sviluppo e sopravvivenza di uova di Idaea inquinata (Scopoli) (Lepi-
doptera Geometridae) a diverse temperature e umidità.
Idaea inquinata (Scopoli) si sviluppa principalmente su piante essiccate, tuttavia 
è un potenziale infestante di cereali e derivati. La biologia di questa specie è poco 
conosciuta, in particolare non ci sono informazioni sull’influenza di temperatura e 
umidità relativa sulla schiusura delle uova. 
Gruppi di 100 uova deposte da 24-48 ore sono state poste a temperature costanti (13, 
15, 36, e 38±1 °C), due diversi valori di umidità relativa (35, 70±5%) e fotoperiodo 
0:24 (Luce:Buio); sono state condotte otto prove, replicate quattro volte. Il numero 
più basso di uova schiuse è stato osservato a 15 °C (9,5) e 36 °C (8,7) con 35±5% 
U.r. mentre a 13 e 38 °C le uova non sono schiuse. Una funzione non lineare è stata 
impiegata per rappresentare il tasso di sviluppo e la sopravvivenza delle uova alle 
due umidità considerando il limite inferiore e superiore di temperatura.

Key words: eggs hatching, Temperature, relative humidity, rusty wave moth

INTroDUCTIoN

Idaea inquinata (Scopoli) can be a serious pest in warehouses where dehydrated 
plants and cereals are stored; spices and medicinal plants can be heavily damaged and 
made unsuitable to essential oil extraction (Candura 1931a, b; Locatelli et al., 2005).



Journal of entomological and acarological research, Ser. II, 42 (3), 2010154

There are few references to the biology of this species (Candura 1931a; Locatelli et 
al., op.cit.). according to Candura, each female laid one hundred eggs within a week, 
oviposition started on the 4th and lasted until the 11th day. eggs were laid singly or in 
pairs, and hatching occurred between the 4th and the 15th day, according to the season 
and to the weather, in a temperature range of 19-28 °C. Limonta et al. (2010) studied 
egg hatching at five temperature and two values of relative humidity, observing that 
I. inquinata tolerates a low relative humidity and high temperatures; in fact, high per-
centages of eggs hatched even at 34 °C at both relative humidities tested (35 and 70% 
r.H.). With 35% and 70% r.H., at 29 and 34 °C, the hatching period was the same but 
was shorter at 17, 21, 26 °C. at 17 °C, both at 35 and 70% r.H., a lower egg hatch and 
longer hatching period was observed. a significantly higher number of hatched eggs was 
observed at 26 and 29 °C at 70% r.H.

This paper deals with eggs development and survival at different temperatures and 
two humidity levels, tests were carried out in order to identify the thermal thresholds. 
The results are a contribution to the development of an integrated pest management 
system in warehouses.

MaTerIaLS aND MeTHoDS

Idaea inquinata has been reared continuously for 6 years, on an artificial diet1 in a 
thermostatic chamber at 26±1°C, 70±5% r.H. and photoperiod of 16:8 (Light:Dark). 
Ten newly formed couples were isolated and the number of eggs layed by each female 
was recorded. 

Groups of 100 eggs, were put in Petri dishes (diameter 6 cm) at different temperatures 
and relative humidities. Specifically, 24-48 hours old eggs were used as more tolerant 
to cold than newly layed eggs (Bell, 1975). Tests were carried out at 13, 15, and 36, 
38±1°C with two levels of relative humidity (35 and 70±5%) and a photoperiod of 0:24 
(Light:Dark). each combination of temperature and humidity was replicated four times. 
egg hatching was observed daily. eggs were considered hatched when the young larvae 
successfully chewed emergence holes in the chorion and left the egg shell. observation 
were carried out daily until eggs appeared not viable.

For each level of relative humidity, the data of this and of a previous research 
summarized in the introduction section and published by Limonta et al. (2010) were 
submitted to aNoVa and Duncan’s multiple range test (SPSS 17.0 for Windows and 
Microsoft excel 2003). 

The model of Brière et al. (1999) was used to predict the curvilinear relationship in 
the entire temperature range permitting development 

r(T ) = α T (T − Tmin) (Tmax − T )0.5. (1)

(1) Ingredients: 114 g bran, 61 g corn flour, 55 g wheat flour, 17 g wheat germ, 14 g dried yeast, 85 g 
glycerine, 67 g honey. The diet was stored in polyethylene bags at 6 °C. 



155L. Limonta et al.: Development and survivorship of I. inquinata eggs 

The parameters Tmin, Tmax, α were estimated on the basis of our observations on 
individuals via non-linear least square regression techniques implemented in the SPSS 
Statistics 17.00 software. 

The stage-specific survivorships (ε) between the upper Tmax and the lower Tmin 
thresholds for development is based on the Beta function

ε(T ) = a (T − Tmin)b (Tmax − T )c. (2)
The values of Tmin, Tmax have been obtained from equation 1, while the parameters 

a, b, c were estimated on the basis of our observations on individuals via non-linear 
least square regression techniques implemented in the SPSS Statistics 17.00 software. 

reSULTS

Idaea inquinata eggs are pearly colored, with a netlike pattern, maximum width is 
5/7 of length. When eggs are just laid they adhere by the poles building a short lived 
coil, after a while they split. 

The mean number of eggs laid by a female was 154.3±46.21 (SD), with range 76-
211, and a mean hatching of 82. 8% (72.81-90.65).

Table 1 - Mean number (SD) of eggs of Idaea inquinata (Scopoli) hatched at 13, 15, 17, 21, 26, 
29, 34, 36, 38 and 40 °C, 35 and 70 % R.H. 

°C
% R.H. 

35 70
Mean (SD) Min-max Mean (SD) Min-max

13 0 - 0 -
15   9.5(1.29)a   8-11 25.2(2.75)a 22-28
17* 64.7(7.85)b 57-72 61.5(11.12)b 51-73
21* 83.5(3.87)c 79-88 73.7(7.27)c 63-79
26* 77.5(3.87)c 72-81 91.5(2.38)d 89-94
29* 78.5(3.51)c 75-82 91.0(6.48)d 84-97
34* 79.7(4.27)c 74-83 81.7(5.91)cd 73-86
36   8.7(5.85)a   2-15 15.5(10.78)a   4-30
38 0 - 0 -

35% r.H.: F5,18=199.12 P<0.001; 70% r.H.: F5,18=70.01 P<0.001
*data from Limonta et al., 2010.

eggs hatched in the temperature range 15-36 °C with both the tested value of relative 
humidity (Tab. 1). at 36 °C a limited number of eggs hatched and newly born larvae 
died within few hours and a third of the larvae died when hatching from the egg. at 13 
and 38 °C egg hatching was not observed. 
at 15 °C the mean number of hatched eggs was 9.5±1.29 (SD) with 35% r.H., and 
25.2±2.75 with 70%; at 36 °C the mean number of hatched eggs was 8.7±5.85 (SD) 
with 35% r.H., and 15.5±5.91 with 70%.



Journal of entomological and acarological research, Ser. II, 42 (3), 2010156

Figure  1  -  The  observed  and  predicted  developmental  rates  of  eggs  of  Idaea inqui-
nata (Scopoli) at different temperatures with 35 (a) and 70% r.H. (b). (■▲: our data, 
used  to  parametrize  the  developmental  rate  functions.  The  rates  are  predicted  by 
r(T ) = α T (T − Tmin) (Tmax − T )0.5 with the stage specific parameters (α, Tmin, Tmax) reported in 
Table 2).

a

b



157L. Limonta et al.: Development and survivorship of I. inquinata eggs 

Figure 2 - The observed and predicted stage specific survival of eggs of  Idaea inqui-
nata (Scopoli) at different temperatures. with 35 (a) and 70% r.H. (b). (■▲: our data, 
used  to  parametrize  the  developmental  rate  functions.  The  survival  is  predicted  by  
ε(T ) = a (T − Tmin)b (Tmax − T )c  with the stage specific parameters (a, Tmin, Tmax, b, c) reported in 
Table 2).

a

6



Journal of entomological and acarological research, Ser. II, 42 (3), 2010158

In fig. 1 the observed and predicted developmental rates of eggs of I. inquinata were 
reported and the curves for both the values of relative humidity are similar regarding 
the upper temperature of development (Table 2) and the higher developmental rate (32 
°C), while the lower temperature of development is lower with 70% r.H. Brière et al. 
(1999) model satisfactorily represented the developmental rates.

In fig. 2 the observed and the predicted egg survival at the two values of relative 
humidity are depicted. By visual examination, the survival appears to be better repre-
sented by equation 2 in fig. 2b than in fig. 2a. 

DISCUSSIoN

a higher mean number of hatched eggs of Idaea inquinata (Scopoli) was observed 
with 70% r.H. at the threshold temperatures of 15 and 36 °C. In the case of Ephestia 
kuehniella zeller, Jacob & Cox (1977) found that “humidity has little influence on egg 
development and developmental periods increase only at very low relative humidities”. 

eggs of I. inquinata did not hatch at 13 °C, and this lower threshold is similar to the 
one of Plodia interpunctella (Hübner), that is 13.5 °C (Savov, 1973). In the range 15-36 
°C I. inquinata eggs hatched, as in Ephestia cautella (Walker) that complete embryonic 
development within 14-36 °C (Nawrot, 1979). The thermal thresholds for Ephestia 
figulilella Gregson and E. calidella (Guenee) are within 15 and 36 °C with 70% rH. 
Corcyra cephalonica (Stainton) eggs cannot survive out of the range 17.5-32.5 °C (Cox 
et al., 1981), while Sitotroga cerealella oliver eggs hatch at 35 °C with different values 
of r.H. (Maity et al., 1999).

In I. inquinata at 36 °C, a limited number of eggs hatched, and larvae do not sur-
vived. at 38 °C eggs collapsed, as in Galleria mellonella L. where at 40 °C eggs dried, 
became brownish and did not hatch (Kumar et al., 2009).

results of this study suggest that storing at 13 or at 38 °C can prevent the develop-
ment of the rusty wave moth. The use of high temperatures is not applicable as the 
properties of medicinal plants could be destroyed. 

The equation 1 proposed by Briére et al. (1999) and equation 2 satisfactorily represent 
the developmental rates and the survival of eggs of I. inquinata at different temperatures. 
The same result has been obtained for other insects life stages reported in the literature 

Table 2 - Parameter estimates and standard errors (SE) for the developmental rate (eq. 1) and 
surivival rate (eq. 2) for Idaea inquinata (Scopoli) eggs (Tmin = minimum temperature for develop-
ment and survival, Tmax = maximum temperature for development and survival). 

% 
R.H.

N Tmin [°C]
(SE)

Tmax [°C]
(SE)

α 
(SE)

a
(SE)

b
(SE)

c
(SE)

35 400 11.01
(0.165)

38.65
(0.104)

0.0096
(0.0000015)

0.65
(0.87)

1.634
(0.317)

1.043
(0.212)

70 400 8.86
(0.174)

38.10
(0.069)

0.00008888
(0.0000)

0.77
(0.71)

1.644
(1.043)

0.993
(0.142)



159L. Limonta et al.: Development and survivorship of I. inquinata eggs 

(e.g. Bell, 1975; Maity et al., 1999). In this paper different parameters have been found 
for the to humidity regimes under study. The predicted lower developmental threshold 
is lower at higher humidity, whereas the upper threshold appears to be similar at both 
relative humidities. This indicate that I. inquinata eggs find more suitable conditions at 
higher humidity than at lower values.

Here we assumed that thresholds for survival are equal to the thresholds obtained 
for the developmental rates. This assumption may be justified by the scope of this work, 
but should be revised if a more precise representation of the survival at temperature 
extremes is required.

This paper allows to make some tentative raccomandations on the management 
of this pest. First, in order to prevent development of I. inquinata on medicinal plants, 
they must be stored at temperature below 13 °C, a method economically sustainable. It 
is important to consider the distribution of interstitial space in the plant species and the 
part of the plant stocked as they influence the time necessary to obtain a uniform tem-
perature in the commodity. Second the relationships between developmental rates and 
temperatures as well as humidities can be used as a component in a forecasting system.

reFereNCeS

BeLL C.H., 1975 - effects of temperature and humidity on development of four pyralid moth pests 
of stored products. Journal of Stored Products research, 11 (3/4): 167-175.

Brière J.F., PrACroS P., Le roux A.y., Priere J.S. 1999 - a novel rate model of temperature 
dependent development for arthropods. environmental entomology 28: 22-29.

CAnDurA, G.S., 1931a - Studio sulla Tignola del fieno (Ptychopoda herbariata). (observations 
on the rusty wave moth (Ptychopoda herbariata)). Bollettino di zoologia Generale e agraria 
di Portici 24: 233-266.

CAnDurA, g.S., 1931b - ricerche sugli insetti e sui danni da essi causati ai prodotti dell’economia 
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LiDiA LiMontA, JuLJuS SuLo, DAriA PAtriziA LoCAteLLi - Dipartimento di Protezione dei Sistemi 
agroalimentare e Urbano e valorizzazione delle Biodiversità- DiPSa, Università degli Studi 
di Milano, Via Celoria 2, 20133 Milano - Italy. e-mail: lidia.limonta@unimi.it

accepted 20 December 2010